First, the scholarship on the topic of the history of Israel/Palestine usually frames the different parties as Israelis (or the Yishuv, the pre-1948 Jewish community) and the Palestinians (or the Arabs). Any research into the topic at all and you will find that this is the primary framing. Indeed, this makes much more sense considering that there are Palestinian Christians who were as just involved in these events as their Muslim counterparts. As another clarification, the Palestinian leadership rejected the 1947 UNSCOP proposal that became the basis of the 1947 UN vote on partition, which was decided unilaterally by the UN. The real partition, however, occurred after the 1948 war, and the final borders were decided by the military successes and failures of the different parties.

Leading up to the 1947 UN vote were a myriad of proposals from the Palestinians for a future resolution of the Palestine question. In the immediate aftermath of WWII, the Istiqlal (Independence) party advocated for the strict implementation of the 1939 White Paper, which had provided for Jewish immigration to Palestine for 5 years, after which any immigration would be subject to Palestinian agreement (which would, unsurprisingly, not be forthcoming). This position recognized the Jewish presence in Palestine at that time, but opposed any sort of continued immigration. On the other hand, the Palestine Arab Party (which was the more popular party) advocated for not only the cessation of immigration but the immediate creation of an Arab government to control the whole country.^1

As you may note, neither of these positions resemble anything like 1948 UN partition plan-- only Istiqlal's position recognized the validity of the "Jewish National Home," which, for the Palestinians, was certainly not anything like a state. By the time the Palestine question came before the UN, the Palestine Arab Party and its leader Jamal al-Husayni had reasserted control of the Palestinian leadership. In his testimony before the UN on the 1947 proposal, al-Husayni outlined the basis of Arab opposition to the partition plan, which he based on international law.^2 He denounced all of the inquiries that had been conducted in Palestine, like the one giving rise to the UNSCOP proposal, as "reduc[ing] the national and legal rights of the Palestine Arabs." He claimed that his opposition to the Zionist project was not based on anti-Semitism, arguing that "The Arab world had been one of the rare havens of refuge for the Jews until the atmosphere of neighbourliness had been poisoned by the Balfour Declaration and the aggressive spirit the latter had engendered in the Jewish community..." Al-Husayni disputed Zionist claims based on religion and history, and claimed that the Arabs of Palestine were entitled to an independent state based on the UN Charter since they were in the majority.

Of course, it is difficult to know exactly how representative the Palestinian Arab Party's views were, considering that neither the peasantry nor the emerging bourgeoisie had representation on it; it was essentially a party of Jerusalemite notables. Even so, Charles D. Smith argues that few Palestinians would have agreed to the partition because of the demographics of Palestine at the time. The UNSCOP proposal offered 57% of the land to the future Jewish State, at a time where Arabs outnumbered Jews 2:1. In addition, Jews were heavily concentrated in urban areas, owning only 6% of the total land (although 20% of the cultivable land). The UNSCOP proposal allotted the whole of the Negev desert (whose population was only 1% Jewish) to the future Jewish state, because the committee was convinced by the Zionists' insistence that it was essential to a viable Jewish state.^3 All in all, the Palestinians were on the whole already opposed to any sort of Jewish state in Palestine; the UNSCOP partition proposal was seen as handing over far too much and disproportionately favoring the Yishuv.

Smith, Charles D. Palestine and the Arab-Israeli Conflict: A History with Documents. 9th ed. Boston: Bedford/St. Martin’s, 2017.

1. 172-174

2. 211-212

3. 187-188

Edit: Including corrections provided by /u/ghostofherzl, please see their comments below for more information on the topic.

To add some further context on what Walrus noted, in 1947, two years after the conclusion of the second world war which had resulted in millions of European Jews either murdered or stateless, the United Nations General Assembly had just convened a partition plan for Palestine to mark the end of the British mandate. This proposal, known as Resolution 181, recommended the creation of two separate Palestinian Arab and Jewish states in the region. As noted by American historian William Roger Louis, British Foreign Secretary Ernest Bevin's policy was still premised on the idea that a local Palestinian Arab majority would carry the day and a single binational state would ensue (similar to the white paper of 1939). The Arab High Committee rejected the recommendations of the UN proposal entirely and boycotted June 1947 inquiry. Not only was the carving up of a separate Jewish state in Palestine contrary to said White Paper which their delegates ( Jamal al-Husseini and Musa al-Alami) had reluctantly agreed to just under a decade earlier, but (as noted by Sami Hadawi) in their eyes was inconsistent with the United Nation’s policy of self-determination, which embraced the right of a people who inhabit a land to govern it.

As discussed by Professor John Quigley and Fred J. Khouri, whilst not the fundamental reason for rejecting it, the Palestinian Arab hostility towards this solution was compounded further when it came to the nature of the partition itself. Despite legally owning only 7% of land in Palestine and composing only a third of the population in 1946, the Jewish state would receive most of the region, 55% in total. Including the land that was most suitable for agriculture. This would result in a significant minority of local Palestinian Arabs coming under the dominion of the proposed separate Jewish state. They would also be given the strategically important but agriculturally infertile Negev Desert. The idea being that as more Jewish migrants arrive and expand throughout the region, there would theoretically be sufficient land for them to settle upon and cultivate. When the previously mentioned British foreign minister, Ernest Bevin received the partition proposal, he promptly instructed for it not to be imposed on the Arabs, and thus the matter was vigorously debated in the 1947 parliament but to little avail.

Palestinian historian Walid Khalidi summarised the key reason behind the Arab refusal to accept the terms of the 1947 UN partition in his article on the History of Palestine;

"A compromise by definition is an arrangement acceptable, however grudgingly, to the protagonists. The “partition” of Palestine proposed by the United Nations was no such thing. It was Zionist in inspiration, Zionist in principle, Zionist in substance, and Zionist in most details. The very idea of partition was abhorrent to the Arabs of Palestine and it was against it that they had fought their bitter, desperate, and costly fight in the years 1937-39. Also, “compromise” implies mutual concession. What were the Zionists conceding? You can only really concede what you actually possess. What possessions in Palestine were the Zionists conceding? None at all."

In summary, in the eyes of the Arab states and many muslims in Palestine, the very idea of another group of people settling within the region and carving out their own nation state with little concern for the inhabitants already living there was repulsive. To put it in simple terms, from the point of view of the Palestinians living there, the United Nations partition seemed to take for granted that the tension between the local population’s aspirations for ideas such as self-determination/independence/justice and the existence of a separate Jewish foothold in Palestine did not exist, and did not really need to be negotiated.

As noted by Baylis Thomas, this assumption was best exemplified by US President Harry Truman's own memoirs on the subject.

"I was fully aware of the Arab hostility to Jewish settlement in Palestine, but like many Americans, I was troubled by the plight of the Jewish people in Europe. The Balfour declaration, promising Jews the opportunity to reestablish a homeland in Palestine, always seemed to me to go hand in hand with the noble policies of Woodrow Wilson, especially the principle of self determination"

Essentially, the Wilsonian concept of self-determination embraced the right of the people who inhabit a land to govern that land. On the other hand, in the eyes of Truman (and the United Nations), was it not obvious that the persecuted and stateless Jews also had a right to self-determination whilst not inhabiting that land?

But Truman avoided the question which the concept of self-determination was supposed to answer; Do a people have the right to declare dominion over land inhabited by others? In service of this avoidance, he, similar to the Zionists in support of a separate Jewish state, acted as though Palestine was not inhabited, or not importantly so. Thus, the idea of carving up a state in Palestine as a homeland for the settlement of another group of people, fundamentally failed to consider the concrete particulars concerning its existing inhabitants. Leading to most of Arab states and Palestinian Arab organisations to reject it.

Sources + Further reading:

William Roger Louis, Ends of British Imperialism: The Scramble for Empire, Suez, and Decolonization. (2006)

Sami Hadawi, Bitter Harvest: A Modern History of Palestine (1989)

John B. Quigley "Palestine and Israel: a challenge to justice" (1990)

Fred J. Khoury, 'United States Peace Efforts', ( Elusive Peace in the Middle East, 1975)

"History of Palestine", Encyclopædia Britannica, article by Walid Ahmed Khalidi & Ian J. Bickerton (2002)

Michael Joseph Cohen "Truman and Israel" University of California Press (1990)

Baylis Thomas, How Israel was Won: A Concise History of the Arab-Israeli Conflict (1999)