He was my student, but now he has become so proficient that it can be said 'the student has surpassed his teacher.'

He is truly demonstrating talent that surpasses his master, just as the saying 'the student has surpassed his or her teacher' goes.

He quoted the proverb 'Once a word leaves your mouth, you cannot chase it back even with the swiftest horse' to teach me to choose my words carefully.