Anas reported this hadlth through another chain of transmitters and the words are:" It would be said to him: You have told a lie; what had been demanded from you was quite easier than this (the belief in the Oneness of Allah)."
وَحَدَّثَنَا عَبْدُ بْنُ حُمَيْدٍ، حَدَّثَنَا رَوْحُ بْنُ عُبَادَةَ، ح وَحَدَّثَنِي عَمْرُو بْنُ زُرَارَةَ، أَخْبَرَنَا عَبْدُ الْوَهَّابِ، - يَعْنِي ابْنَ عَطَاءٍ - كِلاَهُمَا عَنْ سَعِيدِ بْنِ أَبِي عَرُوبَةَ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم بِمِثْلِهِ غَيْرَ أَنَّهُ قَالَ " فَيُقَالُ لَهُ كَذَبْتَ قَدْ سُئِلْتَ مَا هُوَ أَيْسَرُ مِنْ ذَلِكَ " .
Muslim
Characteristics of the Day of Judgment, Paradise, and Hell • Hadith 40