Commenting on verse 29 of surah al-Hud (And, O my people, I do not demand from you any wealth for it) Hakim al-Umma Mawlana Ashraf Ali Thanawi (Allah have mercy on him) said:

Spiritual leaders (Shuyukh) should adopt the same demeanor.

Seeking monetary gain is one of the strongest impediments in imparting religious instructions. In my opinion, it is grossly inappropriate for the Shuyukh to raise charitable funds by asking for donations.

(In general) intelligence is scarce (among people). Stinginess and greed overwhelms (most individuals). They become distrustful (of the individual raising funds) of love of the worldly (hubb-e-duniya) by slightest suspicion. And (it must be remembered that) Allah is the sponsor of (all) charities (in reality). They are not dependent on our appeals of donation and fund raising.”

Masail e sulook min Kalam Malik ul mulook, page 259, Idara-e-Islamiyat, Lahore