Quran 18:23 — The Cave (Al-Kahf)

You shall not say that you will do anything in the future,

[18:22] Some would say, "They were three; their dog being the fourth," while others would say, "Five; the sixth being their dog," as they guessed. Others said, "Seven," and the eighth was their dog. Say, "My Lord is the best knower of their number." Only a few knew the correct number. Therefore, do not argue with them; just go along with them. You need not consult anyone about this.

[18:24] without saying, "GOD willing."* If you forget to do this, you must immediately remember your Lord and say, "May my Lord guide me to do better next time."