A Pearl of Wisdom by Abū Tālib al-Makkī

Abū Tālib al-Makkī relates the following:

وقال بعض العلماء: تعلم لاأدري ولا تتعلم أدري فإن قلت لاأدري علموك حتى تدري وإن قلت أدري سألوك حتى لا تدري

Some scholars have mentioned: Learn how to say “I do not know” and do not learn to say “I know”. For if you say “I do not know”, they will teach you until you know. And if you say “I know”, they will ask you until you do not know.

Qūt al-Qulūb fī Muʿāmalāt al-Maḥbūb 1/172