ʿAbdullāh b. Masʿūd – Allāh be pleased with him – said:

The people will not cease to be well as long as they take knowledge from their seniors. When they take it from their juniors and their bad people, they will be destroyed.

Ibn ʿAbd Al-Barr, Jāmiʿ Bayān Al-ʿIlm article 1057.

Al-Firyābī reports:

When Sufyān [Al-Thawrī] would see these rabble writing knowledge his face would change (in anger). So I asked him, ‘O Abū ʿAbdillāh, we notice that when you see these people writing knowledge, it is hard upon you.’ He replied, ‘Knowledge used to be with the Arabs and with the leaders of the people, but when it left them and went to these types – meaning the rabble of society – the religion was changed.’

Op. cit. article 1072.