"And Allah did not make it," meaning: the reinforcement, "except as a glad tiding for you," so that you may rejoice in it and be happy.
﴿وَمَا جعله الله﴾ يَعْنِي: المدد ﴿إِلا بُشْرَى لَكُمْ﴾ تستبشرون بهَا وتفرحون