Yunus 10:94

فَإِن كُنتَ فِى شَكٍّ مِّمَّآ أَنزَلْنَآ إِلَيْكَ فَسْـَٔلِ ٱلَّذِينَ يَقْرَءُونَ ٱلْكِتَـٰبَ مِن قَبْلِكَ ۚ لَقَدْ جَآءَكَ ٱلْحَقُّ مِن رَّبِّكَ فَلَا تَكُونَنَّ مِنَ ٱلْمُمْتَرِينَ

Fa-in kunta fī shakkin mimmā anzalnā ilayka fasali alladhīna yaqraūna l-kitāba min qablika laqad jāaka l-ḥaqu min rabbika falā takūnanna mina l-mum'tarīna

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.