Giving or zakat is one of the pillars of Islam. It is founded upon this verse in the Quran.
Surah 2:83. And remember We took a covenant from the Children of Israel (to this effect): Worship none but Allah. treat with kindness your parents and kindred, and orphans and those in need; speak fair to the people; be steadfast in prayer; and practice regular charity. Then did ye turn back, except a few among you, and ye backslide (even now).
Dialog: Christians can share with their Muslim friends that giving is also prescribed in the Bible.
Leviticus 27:30 (NIV) “‘A tithe (i.e. tenth) of everything from the land, whether grain from the soil or fruit from the trees, belongs to the LORD; it is holy to the LORD.