ٱلَّذِينَ ءَاتَيْنَـٰهُمُ ٱلْكِتَـٰبَ يَعْرِفُونَهُۥ كَمَا يَعْرِفُونَ أَبْنَآءَهُمُ ۘ ٱلَّذِينَ خَسِرُوٓا۟ أَنفُسَهُمْ فَهُمْ لَا يُؤْمِنُونَ Qur’an Al-An'am (6:20)Alla th eena a tayn a humu alkit a ba yaAArifoonahu kam a yaAArifoona abn a ahum alla th eena khasiroo anfusahum fahum l a yuminoon a
I.e., the truth of God's transcendental uniqueness and oneness, which is stressed in all authentic scriptures.
Cf. ii. 146 and n. 151. In both passages the pronoun translated "this" may mean "him" and refer to Muhammad the Apostle of God, as some commentators think.