Because Allah Almighty has denied the attainment of virtue for the person who does not give charity from his favorite wealth. Allah Almighty says: «‏‏‏‏لَن تَنَالُوا الْبِرَّ حَتَّىٰ تُنفِقُوا مِمَّا تُحِبُّونَ ۚ وَمَا تُنفِقُوا مِن شَيْءٍ فَإِنَّ اللَّـهَ بِهِ عَلِيمٌ» ‏‏‏‏ [ آل عمران: 92] "You will never attain righteousness until you spend in the way of Allah from that which you love."

Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates that when this verse was revealed «‏‏‏‏لَن تَنَالُوا الْبِرَّ حَتَّىٰ تُنفِقُوا مِمَّا تُحِبُّونَ» ‏‏‏‏ [ سورة آل عمران: 92 ] , Sayyiduna Abu Talhah (may Allah be pleased with him) came to the service of the Noble Prophet (peace and blessings be upon him) while he was sitting on the pulpit. He said, "O Messenger of Allah (peace and blessings be upon him), of all my gardens, the garden of Bairuha is the most beloved to me." So the Noble Prophet said, "Bairuha is perishable wealth (while its reward will remain), or he said, Bairuha is a very profitable garden." The narrator is unsure about this. So Sayyiduna Abu Talhah (may Allah be pleased with him) said, "I seek the nearness of Allah Almighty through this garden." The Prophet (peace and blessings be upon him) said, "Distribute it among your relatives." Thus, Sayyiduna Abu Talhah (may Allah be pleased with him) distributed the orchards of this garden among his relatives. I have mentioned the narration of Thabit and Humaid bin Anas elsewhere.