6:54
وَإِذَا جَآءَكَ ٱلَّذِينَ يُؤْمِنُونَ بِـَٔايَـٰتِنَا فَقُلْ سَلَـٰمٌ عَلَيْكُمْ ۖ كَتَبَ رَبُّكُمْ عَلَىٰ نَفْسِهِ ٱلرَّحْمَةَ ۖ أَنَّهُۥ مَنْ عَمِلَ مِنكُمْ سُوٓءًۢا بِجَهَـٰلَةٍ ثُمَّ تَابَ مِنۢ بَعْدِهِۦ وَأَصْلَحَ فَأَنَّهُۥ غَفُورٌ رَّحِيمٌ
And when those come to you who believe in Our verses, say, "Peace be upon you. Your Lord has decreed upon Himself mercy: that any of you who does wrong out of ignorance and then repents after that and corrects himself - indeed, He is Forgiving and Merciful."
Context in Surah Al-An'am
Nearby ayahs help place verse 6:54 in sequence and meaning.
وَلَا تَطْرُدِ ٱلَّذِينَ يَدْعُونَ رَبَّهُم بِٱلْغَدَوٰةِ وَٱلْعَشِىِّ يُرِيدُونَ وَجْهَهُۥ ۖ مَا عَلَيْكَ مِنْ حِسَابِهِم مِّن شَىْءٍ وَمَا مِنْ حِسَابِكَ عَلَيْهِم مِّن شَىْءٍ فَتَطْرُدَهُمْ فَتَكُونَ مِنَ ٱلظَّـٰلِمِينَ
And do not send away those who call upon their Lord morning and afternoon, seeking His countenance. Not upon you is anything of their account and not upon them is anything of your account. So were you to send them away, you would [then] be of the wrongdoers.
وَكَذَٰلِكَ فَتَنَّا بَعْضَهُم بِبَعْضٍ لِّيَقُولُوٓا۟ أَهَـٰٓؤُلَآءِ مَنَّ ٱللَّهُ عَلَيْهِم مِّنۢ بَيْنِنَآ ۗ أَلَيْسَ ٱللَّهُ بِأَعْلَمَ بِٱلشَّـٰكِرِينَ
And thus We have tried some of them through others that the disbelievers might say, "Is it these whom Allah has favored among us?" Is not Allah most knowing of those who are grateful?
وَكَذَٰلِكَ نُفَصِّلُ ٱلْـَٔايَـٰتِ وَلِتَسْتَبِينَ سَبِيلُ ٱلْمُجْرِمِينَ
And thus do We detail the verses, and [thus] the way of the criminals will become evident.
قُلْ إِنِّى نُهِيتُ أَنْ أَعْبُدَ ٱلَّذِينَ تَدْعُونَ مِن دُونِ ٱللَّهِ ۚ قُل لَّآ أَتَّبِعُ أَهْوَآءَكُمْ ۙ قَدْ ضَلَلْتُ إِذًا وَمَآ أَنَا۠ مِنَ ٱلْمُهْتَدِينَ
Say, "Indeed, I have been forbidden to worship those you invoke besides Allah." Say, "I will not follow your desires, for I would then have gone astray, and I would not be of the [rightly] guided."