The Family Of Imran - 3:164
Allah was gracious in sending from among the believers a messenger who recited to them His Verses, purified them and taught them the Book and wisdom. But they were in manifest error before!
The most important criterion of belief:
The Cattle/6:82
Those who believe and do not mix their faith with wrongdoing, they deserve security and they have found the truth.
اَلَّذ۪ينَ اٰمَنُوا وَلَمْ يَلْبِسُٓوا ا۪يمَانَهُمْ بِظُلْمٍ اُو۬لٰٓئِكَ لَهُمُ الْاَمْنُ وَهُمْ مُهْتَدُونَ۟
Luqman/31:13
"When Lokman advised his son, he said: "My dear son, do not associate partners with Allah; surely shirk (associating partners with God) is a great wrong."
وَاِذْ قَالَ لُقْمٰنُ لِابْنِه۪ وَهُوَ يَعِظُهُ يَا بُنَيَّ لَا تُشْرِكْ بِاللّٰهِۜ اِنَّ الشِّرْكَ لَظُلْمٌ عَظ۪يمٌ
The Companies/39:65
It has been revealed to you and those before you that if you associate partners, all that you do will be in vain and you will be of the losers.
وَلَقَدْ اُو۫حِيَ اِلَيْكَ وَاِلَى الَّذ۪ينَ مِنْ قَبْلِكَۚ لَئِنْ اَشْرَكْتَ لَيَحْبَطَنَّ عَمَلُكَ وَلَتَكُونَنَّ مِنَ الْخَاسِر۪ينَ