Concise Quran Commentary
So when they submitted to Allah and obeyed him, Abraham laid his son down on his forehead, to carry out the order given to him to slaughter his son.
فَلَمَّآ أَسْلَمَا وَتَلَّهُۥ لِلْجَبِينِ
When they both submitted [to Allah’s command] and Abraham laid him on his forehead,
So when they submitted to Allah and obeyed him, Abraham laid his son down on his forehead, to carry out the order given to him to slaughter his son.