﴿ وَمَا جَعَلَهُ ٱللَّهُ إِلَّا بُشْرَىٰ لَكُمْ وَلِتَطْمَئِنَّ قُلُوبُكُم بِهِۦ ۗ وَمَا ٱلنَّصْرُ إِلَّا مِنْ عِندِ ٱللَّهِ ٱلْعَزِيزِ ٱلْحَكِيمِ ﴾

“And God ordained this [to be said by His Apostle] only as a glad tiding for you, and that your hearts should thereby be set at rest - since no succour can come from any save God, the Almighty, the Truly Wise -”

Please check ayah 3:129 for complete tafsir.