The Quran

۞ وَمِن أَهلِ الكِتابِ مَن إِن تَأمَنهُ بِقِنطارٍ يُؤَدِّهِ إِلَيكَ وَمِنهُم مَن إِن تَأمَنهُ بِدينارٍ لا يُؤَدِّهِ إِلَيكَ إِلّا ما دُمتَ عَلَيهِ قائِمًا ۗ ذٰلِكَ بِأَنَّهُم قالوا لَيسَ عَلَينا فِي الأُمِّيّينَ سَبيلٌ وَيَقولونَ عَلَى اللَّهِ الكَذِبَ وَهُم يَعلَمونَ

Muhammad Asad

AND AMONG the followers of earlier revelation there is many a one who, if thou entrust him with a treasure, will [faithfully] restore it to thee; and there is among them many a one who, if thou entrust him with a tiny gold coin, will not restore it to thee unless thou keep standing over him - which is an outcome of their assertion,¹ "No blame can attach to us [for anything that we may do] with regard to these unlettered folk": and [so] they tell a lie about God, being well aware [that it is a lie]."²

Lit., "this, because they say". In Arabic usage, the verb qala (lit., "he said") often signifies "he asserted" or "expressed an opinion". As is evident from many Traditions, the people referred to are the Jews.
I.e., they falsely claim that God Himself has exempted them from all moral responsibility towards non-Jews (contemptuously described as "unlettered folk"), knowing well that their own scriptures provide no basis whatever for such a claim.