Surah At-Tawbah, Verse 43

عَفَا ٱللَّهُ عَنكَ لِمَ أَذِنتَ لَهُمۡ حَتَّىٰ يَتَبَيَّنَ لَكَ ٱلَّذِينَ صَدَقُواْ وَتَعۡلَمَ ٱلۡكَٰذِبِينَ٤٣

ʿafā l-lahu ʿanka lima adhinta lahum ḥattā yatabayyana laka alladhīna ṣadaqū wataʿlama l-kādhibīna

Allāh has pardoned you, [O Muḥammad, but] why did you give them permission [to remain behind]? [You should not have] until it was evident to you who were truthful and you knew [who were] the liars.