فَإِن كُنتَ فِي شَكّٖ مِّمَّآ أَنزَلۡنَآ إِلَيۡكَ فَسۡـَٔلِ ٱلَّذِينَ يَقۡرَءُونَ ٱلۡكِتَٰبَ مِن قَبۡلِكَۚ لَقَدۡ جَآءَكَ ٱلۡحَقُّ مِن رَّبِّكَ فَلَا تَكُونَنَّ مِنَ ٱلۡمُمۡتَرِينَ ٩٤
Fa in kunta fī shakkim mimmā anzalnā ilayka fas'alil-ladhīna yaqra'ūnal-kitāba min qablika laqad jā'akal-haqqu mir rabbika falā takūnanna minal-mumtarīn
So if you are in doubt, [O Muḥammad], about that which We have revealed to you, then ask those who have been reading the Scripture before you. The truth has certainly come to you from your Lord, so never be among the doubters.