Side questions. Did any Vikings convert to Islam? Were there any "famous" Muslim viking?
While on this topic I wonder if there were any Muslims who converted to Norse Paganism ? I can imagine a few Muslim warriors who would find the idea of Valhalla quite appealing. I hope this question doesn't veer too far off the original one.
"You Arabs are a bunch of idiots", he said. I asked him why.
He said: "Because you was those who were the most beloved and noble amongst you, and then you put them in the ground for the earth and vermin to consume them; whereas we burn them and in an instant they reach Paradise"
The quote above is from possibly the only primary source describing possible contact between Muslims and Vikings the well-known travelogue of Ibn Fadlān, who was sent as an ambassador to Central Asia. It must be noted that the majority of the Arabic sources that speak of the same subject are more interested in describing how they saw the Vikings, rather than vice versa. As far as I know, Ibn Faḍlan's Riḥla is the only attestation of an actual conversation between Muslims and Vikings.
As we know, the Vikings frequently travelled along the Wolga river all the way down to the Black Sea; a number of these were also enlisted in the Byzantine Varangian Guard, which was entirely composed of Norsemen.
However, the term encountered in the Arabic sources (Rūs(iyya)) is not entirely free from ambivalence: James Montgomery argues that the term was not applied for any specific group, but rather any peoples from the north engaging in trade and military activities. Regardless, there are some indications that Ibn Faḍlān is indeed talking aobut Vikings:
It is likely that he a group of Vikings somewhere in the area of modern-day Astrakhan oblast, or at least somewhere along the Volga river (*wa raʾaytu al-rūsiyya wa nazalū ʿalā nahri ʾitil). What's particularly interesting about this encounter is that he gives an accurate description of Viking burial rituals, which are corroborated by sources from the other side of Europe (perhaps an expert on Viking expeditions in western Europe can attest to this?).
In any case, Ibn Faḍlān of course mostly provides information as to how the Vikings were seen by Muslims, rather than the other way around. It's evident that Muslim writers were intrigued by the liberal behaviour of Vikings they encountered, particularly the civil independence of women and the openness with with sexual relations were conducted. Moreover, Ibn Faḍlān was horrified by the lack of hygiene of the men he encountered, stating:
"they are the most filthy of God's creations and do not wash themselves after defecating nor after sexual intercourse, nor do they clean their hands after they have eaten" Riḥlat Ibn Faḍlān, 151
From what I understand, this actually contradicts with what we know about Vikings; again, an expert on Viking social customs should probably comment on this. On a more positive note, Ibn Faḍlān was very much impressed by the physique and strength of the men he encountered, stating that he "had never seen more perfect physiques".
So what can we actually learn from this? There is next to nothing in Ibn Faḍlāns Riḥla apart from the initial quote I gave that describes how Vikings saw Muslims. It's possible that the Vikings considered Muslim tendencies towards ritual cleanliness and abstention from sex and alcohol to be (x,y,z), but apart from a single comment about burial customs, we don't really know much about Viking perspectives on Islam (at least not from the Islamic sources).
TL;DR: Vikings thought the Muslim burying of people is cray-cray
Sources
Ibn Faḍlān (1974), Rihla. Edited by Sami Dahhān
Golden, P.B. (1970) "Rūs". In Volume 8 of The Encyclopaedia of Islam, Second Edition
Montgomery, J. (2000) Ibn Faḍlān and the Rūsiyyah
Canard, M. "Ibn Faḍlān". In Volume 3 of The Encyclopaedia of Islam