Abu Dhar Ghifari. was an eminent companion of the Holy Prophet and was among the early converts to Islam. His original name was Jandab b Janadah, and he belonged to the Ghifari tribe who had their settlements between Makkah and Syria. The Ghifari tribe was converted to Islam through the efforts of Abu Dhar Ghifari. When the Holy Prophet migrated to Madina, Abu Dhar also came to Madina, and there devoted himself exclusively to prayers and religious meditation. He adopted a more or less ascetic way of life, shunned luxury, and stood for austerity. He is described as the first socialist in Islam. After the death of the Holy Prophet he went to Syria, and undertook Jihad. He was outspoken and he freely criticized the administration where he felt that there was anything wrong. The Holy Prophet said of him that nothing could deter him from speaking whatever he considered to be the truth.
"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