God is pleased with the believers who pledged allegiance to you under the tree. He knew what was in their hearts and, consequently, He blessed them with contentment, and rewarded them with an immediate victory.
لَقَد رَضِىَ اللَّهُ عَنِ المُؤمِنينَ إِذ يُبايِعونَكَ تَحتَ الشَّجَرَةِ فَعَلِمَ ما فى قُلوبِهِم فَأَنزَلَ السَّكينَةَ عَلَيهِم وَأَثٰبَهُم فَتحًا قَريبًا
laqad radiyal laahu ‘anil mu’mineena iz yubaayi ‘oonaka tahtash shajarati fa’alima maa fee quloobihim fa anzalas sakeenata ‘alaihim wa asaa bahum fat han qareebaa