Read Surah An-Nisaa 4:136: "O you who have attained to faith! Hold fast unto your belief in God and His Apostle, and in the divine writ which He has..." Full Arabic text, English translation, and image generator.
يَا أَيُّهَا الَّذِينَ آمَنُوا آمِنُوا بِاللَّهِ وَرَسُولِهِ وَالْكِتَابِ الَّذِي نَزَّلَ عَلَىٰ رَسُولِهِ وَالْكِتَابِ الَّذِي أَنْزَلَ مِنْ قَبْلُ ۚ وَمَنْ يَكْفُرْ بِاللَّهِ وَمَلَائِكَتِهِ وَكُتُبِهِ وَرُسُلِهِ وَالْيَوْمِ الْآخِرِ فَقَدْ ضَلَّ ضَلَالًا بَعِيدًا
O you who have attained to faith! Hold fast unto your belief in God and His Apostle, and in the divine writ which He has bestowed from on high upon His Apostle, step by step, as well as in the revelation which He sent down aforetime: for he who denies God, and His angels, and His revelations, and His apostles, and the Last Day, has indeed gone far astray.