If you're referring to his speech at Clermonts in 1095, there are a few different versions. The two earliest versions are from the Gesta Francorum, an anonymous chronicle from around the turn of the 12th century, and Fulcher of Chartres, who wrote another chronicle during the early 12th century. The general consensus is that Fulcher was definitely an eyewitness at the speech itself, so I'll refer to his version, but keep in mind there's some contention about the specific contents of the speech and no way to reliably confirm which are the 'correct' versions.

Much of the speech is unrelated to the Crusade, but in the final part Urban calls for all men, whether noble or commoner, to travel to the Holy Land to aid Christians in the east. He states that any who take part in this 'pilgrimage' (as the term Crusade didn't exist) would be granted "immediate remission of sins". He justifies this action by stating that "Christ commands it".

Here's a link to the speech, so you can have a more detailed look for yourself. https://sourcebooks.fordham.edu/source/urban2-5vers.html