After the fall of Makkah, the Holy Prophet sent a mission to the neighboring tribes of Hawazin and Thaqueef, inviting them to accept Islam. They rejected the invitation and chose the warpath, boasting that they were not cowards like the Quraish of Makkah. The two tribes along with their allies mustered in considerable strength at Autas a few miles to the east of Makkah on the way to Taif. The coalition was led by Malik b Auf, a fiery commander of considerable skill.
"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