Surah Al Hajj Tafseer

Allah will judge between you on the Day of Resurrection about that wherein you used to differ.

This is like the Ayah:

فَلِذَلِكَ فَادْعُ وَاسْتَقِمْ كَمَأ أُمِرْتَ وَلَا تَتَّبِعْ أَهْوَاءَهُمْ وَقُلْ ءَامَنتُ بِمَأ أَنزَلَ اللَّهُ مِن كِتَـبٍ

So unto this then invite, and stand firm as you are commanded, and follow not their desires but say:"I believe in whatsoever Allah has sent down of the Book." (42:15)