Al-Hasan Al-Basrī – Allah have mercy on him – said:

When a man sought knowledge, it would not be long before it could be seen in his humbleness, his sight, upon his tongue and his hands, in his prayer, in his speech and in his disinterest (zuhd) in worldly allurements. And a man would acquire a portion of knowledge and put it into practice, and it would be better for him than the world and all it contains – if he owned it he would give it in exchange for the hereafter.

Ibn Al-Mubārak, Al-Zuhd wa Al-Raqā`iq Vol.1 p.156.