Zakah is the third pillar of Islam that requires Muslims to give 2.5% of their savings each year to the poor and needy. The document discusses that zakah is an obligatory act of faith mentioned frequently in the Quran, showing its importance of sharing wealth. In addition to zakah, Muslims can do optional charity or sadaqah through kind acts and donations to earn spiritual rewards, such as smiling at others, cleaning public areas, and helping those in need.