يَـٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوٓا۟ إِن تَنصُرُوا۟ ٱللَّهَ يَنصُرْكُمْ وَيُثَبِّتْ أَقْدَامَكُمْ
Yaaa ayyuhal lazeena aamanooo in tansurul laaha yansurkum wa yusabbit aqdaamakum
اے اہل ایمان! اگر تم خدا کی مدد کرو گے تو وہ بھی تمہاری مدد کرے گا اور تم کو ثابت قدم رکھے گا
You who believe, if you support God, he will support you and make your steps firm.
God is named as the one who receives support here, which commentators take as support for his cause and his Messenger, and the surah's setting is a battle line. The second half of the promise is bodily: feet made firm. That is what people standing in ranks actually need, and it comes after the commitment, so the steadiness described is granted in the standing itself.