If one doubts whether he said the takbir of ihram, does he repeat it or what does he do?

Question:
Honorable Shaykh, may Allah grant you success, if I prayed and recited al-Fatihah and I did not know whether I had said the takbir of ihram or not, do I break my prayer and say the takbir again, or what do I do?

Answer:
If this is a constant state for you, it is waswas (whispers of Shaytan), so leave it. But if it happens to you occasionally and you do not have waswas, then you must say the takbir of ihram, because it is a pillar of the prayer and one must be certain of having performed it. However, if this persists with you and this is waswas, you leave it. Yes.