Surah Yunus 10:51

أَثُمَّ إِذَا مَا وَقَعَ ءَامَنتُم بِهِۦٓ ۚ ءَآلْـَٔـٰنَ وَقَدْ كُنتُم بِهِۦ تَسْتَعْجِلُونَ

Then is it that when it has [actually] occurred you will believe in it? Now? And you were [once] for it impatient.

Translation: Saheeh International

Tafsir

Is it only then when it has come to pass when it has befallen you that you will believe therein? that is in God or it means in the chastisement when it has come down the use of hamza in a-thumma ‘is it then’ is to deny the possibility of deferrment of chastisement in other words it your belief will not be accepted …

Excerpt from Tafsir al-Jalalayn, commentary on 10:51, via Quran.com. The reader has the full commentary and 9 more tafsirs.