Verse 13

فَرَدَدْنَـٰهُ إِلَىٰٓ أُمِّهِۦ كَىْ تَقَرَّ عَيْنُهَا وَلَا تَحْزَنَ وَلِتَعْلَمَ أَنَّ وَعْدَ ٱللَّهِ حَقٌّ وَلَـٰكِنَّ أَكْثَرَهُمْ لَا يَعْلَمُونَ

We therefore returned him to his mother to brighten her eyes, and remove her sadness and in order for her to know that indeed God’s promise is the truth, but most of them do not know.