إِن يَنصُرْكُمُ ٱللَّهُ فَلَا غَالِبَ لَكُمْ ۖ وَإِن يَخْذُلْكُمْ فَمَن ذَا ٱلَّذِى يَنصُرُكُم مِّنۢ بَعْدِهِۦ ۗ وَعَلَى ٱللَّهِ فَلْيَتَوَكَّلِ ٱلْمُؤْمِنُونَ
Iny-yansurkumul laahu falaa ghaaliba lakum wa iny-yakhzulkum faman zal lazee yansurukum mim ba'dih; wa 'alal laahi falyatawakkalil mu'minoon
Jika Allah menolong kamu, maka tak ada orang yang dapat mengalahkan kamu; jika Allah membiarkan kamu (tidak memberi pertolongan), maka siapakah gerangan yang dapat menolong kamu (selain) dari Allah sesudah itu? Karena itu, hendaklah kepada Allah saja orang-orang mukmin bertawakal.
If God helps you, none can overcome you; and if he forsakes you, who then can help you after him? In God let the believers place their trust.
Uhud is the background here. The verse before this had the Prophet told to consult his companions and then, once resolved, to trust, so the trust described is what follows a decision rather than a substitute for making one. Khadhala, the verb used for God withholding help, is the ordinary Arabic word for deserting someone in the middle of a fight, which is precisely what had just happened at Uhud.