Surah At-Tawbah 9:75

۞ وَمِنْهُم مَّنْ عَـٰهَدَ ٱللَّهَ لَئِنْ ءَاتَىٰنَا مِن فَضْلِهِۦ لَنَصَّدَّقَنَّ وَلَنَكُونَنَّ مِنَ ٱلصَّـٰلِحِينَ

And among them are those who made a covenant with Allāh, [saying], "If He should give us from His bounty, we will surely spend in charity, and we will surely be among the righteous."

Translation: Saheeh International

Tafsir

And some of them have made a covenant with God saying ‘If He gives us of His bounty we will give voluntary alms la-nassaddaqanna the original tā’ of natasaddaqanna has been assimilated with the sād and become of the righteous’ this was Tha‘laba b. …

Excerpt from Tafsir al-Jalalayn, commentary on 9:75, via Quran.com. The reader has the full commentary and 9 more tafsirs.