Surah Al-Fath 48:18

۞ لَّقَدْ رَضِىَ ٱللَّهُ عَنِ ٱلْمُؤْمِنِينَ إِذْ يُبَايِعُونَكَ تَحْتَ ٱلشَّجَرَةِ فَعَلِمَ مَا فِى قُلُوبِهِمْ فَأَنزَلَ ٱلسَّكِينَةَ عَلَيْهِمْ وَأَثَـٰبَهُمْ فَتْحًا قَرِيبًا

Certainly was Allāh pleased with the believers when they pledged allegiance to you, [O Muḥammad], under the tree, and He knew what was in their hearts, so He sent down tranquility upon them and rewarded them with an imminent conquest

Translation: Saheeh International

Tafsir

Verily God was pleased with the believers when they pledged allegiance to you at al-Hudaybiyya under the tree this was an acacia — they these believers numbered 1300 or more; he took an oath of allegiance from them that they would fight against Quraysh and not attempt to flee from death. …

Excerpt from Tafsir al-Jalalayn, commentary on 48:18, via Quran.com. The reader has the full commentary and 9 more tafsirs.