Formal prayer (salat) is the second pillar of Islam, and the most important of a Muslim's acts of worship. Prophet Muhammad (PBUH) said: "The first of one's actions for which a slave of Allah will be held accountable on the Day of Judgment will be one's prayers. If they are correct and accounted for, then he (or she) will have succeeded (gained paradise); and if they are lacking, then he (or she) will have failed (lost paradise).