The statement of al-Imām Aḥmad about al-Qadar:
Not to debate or argue with anyone, and not to learn argumentation.
There are from amongst the small students of knowledge, who go and debate with the Rāfiḍah, the Jaḥmiyyah, and the Muʿtazilah concerning the divine decree, debating with them in these affairs. Do not subject yourself to doubts (for indeed they lead you to being) astray. However, the skillful scholar, who knows that he will be able to benefit from such debates, either aiding the Sunnah or subduing the people of falsehood, or even maybe Allāh will guide the one whom the scholar is debating. If he is seeking the truth, then the scholar is to clarify the issue to him.
As for you, the poor small student who is weak in knowledge, do not debate! I emphasise this point to the students of knowledge that you should not debate concerning the likes of these very serious innovations. As for the normal affairs that you know, and they are to the limits of your abilities, and you fully understand them, then there is no problem for you to discuss them, as long as the intention is not to debate and gain victory, but rather the goal is for clarification.
Source: ‘An Explanation of Imām Aḥmad’s Foundations of the Sunnah’ by Shaykh Rabīʿ ibn Hādī al-Madkhalī, pg.113-114