Al-Allaamah Siddeeq Hasan Khan (rahimahullaah) said:
The aim behind the religious sciences is not for the purpose of earning (wealth); rather it is for (the purpose of) acquainting oneself with the realities of the (sharia) and to rectify one’s behaviour (towards his Lord, the people and within himself). The one who learns knowledge (of the religion) for the purpose of trade cannot be a scholar; rather he only resembles the scholars. Indeed the scholars unveiled what the drive behind this was and they spoke about it when the building of schools reached them at Baghdaad. So they established gatherings of knowledge and said: “The possessors of lofty ambitions and the pure souls used to preoccupy themselves with it (i.e. knowledge) –those whose intent behind (seeking) knowledge was due to its nobility and the perfection (that is reached by way of it), so they came to the scholars to benefit from them and their knowledge. However, when (monetary gain) is placed on it, the vilest people and the lazy ones will approach it and thus leading to its disappearance. So at this juncture the (Islamic) sciences of wisdom (found in the Qur’aan, the Sunnah and the understanding of the Salaf) will be abandoned even though they are self-evident in their nobility.
[أبجد العلوم pages 77-78… Vol: 1]