Mâlik b. Dînâr – Allâh have mercy on him – once said:

Verily you are in greatly troubled times. Only one with true insight knows the times you live in. Verily you are in a time of [people] boasting and being proud. [1] Their tongues are swollen in their mouths, and they seek worldly gain through the deeds of the hereafter. So be warned against them for yourselves, lest they catch you in their nets. O scholar, you are a scholar yet you devour [wealth] with your knowledge. O scholar, you are a scholar yet you boast with your knowledge. O scholar, you are a scholar yet you seek to amass [wealth] with your knowledge. O scholar, you are a scholar yet you transgress [against others] with your knowledge. If you had truly sought this knowledge for Allâh, it would have been seen on you and in your deeds.

[1] The word in some reports is tafâkhur (boasting and being proud) but in some other versions, other somewhat ambiguous words are found in its place.

Abû Bakr Al-Âjurrî, Kitâb Al-‘Âlim Al-Jâhil article 73 et al.