Hawzah News Agency – Imam al-Sadiq peace be upon him says:

مَن لَم يَجْتَنِبْ مُصادقَةَ الأحمَقِ أوْشَكَ أنْ يَتَخلّقَ بأخْلاقِهِ.

'The one who does not refrain from the friendship of a fool will soon adopt his character.'

Source: Amali al-Saduq, p. 222, no. 1