إِذا لَم تَكُن عالِماً بِالسُؤالِ

فَتَركُ الجَوابِ لَهُ أَسلَمُ

If you don't know the question

Leaving the answer is safer

فَإِن أَنتَ شَكَّكتَ فيما سُئِل

تَ فَخيرُ جَوابِكَ لا أَعلَمُ

If you doubt what was asked

Your best answer is: I don't know