Imam Malik said:
“If a debater comes to you, then make clear the sunnah to him but do not debate him”
Shaykh ibnu Uthaymeen comments: Because if you made clear the sunnah to him, then you have placed the proof upon him between his hands (before him). If he then (still) debates, then he is debating Allah (as the proof/sunnah is from Allah) and he is not debating you. So clarify the sunnah to him and refrain from debating about it (the issue), because what is compulsory upon the one whom the sunnah has been made clear to is to accept it without debating.
Tafsir Surah An-Nisaa V.63