Sura al-Nisāʾ 4:105

إِنَّآ أَنزَلْنَآ إِلَيْكَ ٱلْكِتَٰبَ بِٱلْحَقِّ لِتَحْكُمَ بَيْنَ ٱلنَّاسِ بِمَآ أَرَىٰكَ ٱللَّـهُ وَلَا تَكُن لِّلْخَآئِنِينَ خَصِيمًا

innā anzalnā ilayka l-kitāba bil-ḥaqqi li-taḥkuma bayna l-nāsi bimā araka allāhu wa-lā takun lil-khāinīna khaṣīman

We have sent down to thee the Book in truth, that thou mightest judge between men, as guided by Allah: so be not (used) as an advocate by those who betray their trust;