(Al-An'aam) 6 : 54
وَإِذَا جَاءَكَ الَّذِينَ يُؤْمِنُونَ بِآيَاتِنَا فَقُلْ سَلَامٌ عَلَيْكُمْ ۖ كَتَبَ رَبُّكُمْ عَلَىٰ نَفْسِهِ الرَّحْمَةَ ۖ أَنَّهُ مَنْ عَمِلَ مِنْكُمْ سُوءًا بِجَهَالَةٍ ثُمَّ تَابَ مِنْ بَعْدِهِ وَأَصْلَحَ فَأَنَّهُ غَفُورٌ رَحِيمٌ
And whenever those who are believing with Our verses come to you, then you say them: “Peace be upon you”, Your Lord has prescribed Mercy upon Himself, so any of you who commits evil out of ignorance, then repents later on, and reforms, then indeed He (Lord) is the Forgiving, Merciful.
As there is no group of believers anywhere in the world, the odd believer is commanded to follow a lifestyle explained in verses 7: 205-206. See explanation 4: 17-18 and 86.