Once Ali called his slave, but the slave did not respond to his call. He called him thrice, but the slave kept silent. Thereafter Ali went to the slave and said, "Did you not hear my call?" He said that he had heard to his call, but was at that time calling upon God who had subjected him to the humiliation of slavery. Thereupon Ali said, "I release you from slavery forthwith in the name of God."
"When a person dies, his works end, except for three: ongoing charity, knowledge that is benefited from, and a righteous child who prays for him."
Prophet Mohammed (PBUH)
"The best of what a man leaves behind are three: a righteous child who supplicates for him, ongoing charity the reward of which reaches him, and knowledge that is acted upon after him."
Sunan Ibn Mājah
"Every day two angels come down from Heaven and one of them says, 'O Allah! Compensate every person who spends in Your Cause,' and the other (angel) says, 'O Allah! Destroy every miser.'"
Sahih Bukhari