Imaam Bukhaari (rahimahullah) once mentioned the following to Ibnu Abi Haatim (rahimahullah), “My monthly income was five hundred dirhams. I would spend this entire amount in acquiring the knowledge of deen.”
Hearing this, Ibnu Abi Haatim (rahimahullah) remarked, “What a great difference there is between the one who acquires wealth to spend it in the path of deen, and the one who uses the knowledge of deen to acquire the wealth of the world!”
Imaam Bukhaari (rahimahullah) responded by reciting the following verse of the Qur’aan Majeed:
وَ مَا عِنۡدَ اللّٰہِ خَیۡرٌ وَّ اَبۡقٰی
The reward which is by Allah Ta‘ala is better and more-lasting (than the wealth of this world).
(Siyar A’laamin Nubalaa 12/449)
Regarding the manner in which Imaam Bukhaari (rahimahullah) would spend his wealth upon the students of Hadith, Muhammed bin Abi Haatim (rahimahullah) reports:
Imaam Bukhaari (rahimahullah) would spend abundant wealth in charity. When any student of Hadith was in need, he would hold his hand and give him approximately twenty to thirty dirhams, without anyone noticing that he had assisted this person or given him anything. Imaam Bukhaari (rahimahullah) would keep his purse with him at all times (to spend on the needy).
I saw Imaam Bukhaari (rahimahullah), on multiple occasions, giving the same student a bag containing three hundred dirhams. The only reason that I knew of the amount in the bag is that the person himself informed me of it later on.
The student mentioned to me that on one such occasion, Imaam Bukhaari (rahimahullah) gave him a lot of wealth in secret. Thereafter, during the dars of Hadith, the student wished to express his gratitude and make du‘aa for Imaam Bukhaari (rahimahullah) before the other students. However, Imaam Bukhaari (rahimahullah) did not want anyone to come to know of the financial assistance he had given to the student. Therefore, he immediately commanded the student to continue the dars and read the next Hadith which Imaam Bukhaari (rahimahullah) was to teach.”
(Siyar A’laamin Nubalaa 12/450)