The Prophet ﷺ said: It is not allowable for a believer to keep from a believer for more than three days. If three days pass, he should meet him and give him a salutation, and if he replies to it they will both have shared in the reward; but if he does not reply he will bear his sin (according to Ahmad's version) and the one who gives the salutation will have come forth from the sin of keeping apart.

أَنَّ النَّبِيَّ ﷺ قَالَ لاَ يَحِلُّ لِمُؤْمِنٍ أَنْ يَهْجُرَ مُؤْمِنًا فَوْقَ ثَلاَثٍ فَإِنْ مَرَّتْ بِهِ ثَلاَثٌ فَلْيَلْقَهُ فَلْيُسَلِّمْ عَلَيْهِ فَإِنْ رَدَّ عَلَيْهِ السَّلاَمَ فَقَدِ اشْتَرَكَا فِي الأَجْرِ وَإِنْ لَمْ يَرُدَّ عَلَيْهِ فَقَدْ بَاءَ بِالإِثْمِ زَادَ أَحْمَدُ وَخَرَجَ الْمُسَلِّمُ مِنَ الْهِجْرَةِ

[Machine] The Messenger of Allah ﷺ said: "It is not permissible for a believer to forsake another believer for more than three days. And if they meet after three days, one should greet the other. However, if one does not respond, the Muslim who initiated the greeting will be free from the sin of abandoning, and the responsibility will fall upon the one who did not respond."

قَالَ رَسُولُ اللهِ ﷺ لَا يَحِلُّ لِمُؤْمِنٍ أَنْ يَهْجُرَ مُؤْمِنًا فَوْقَ ثَلَاثَةِ أَيَّامٍ فَإِذَا مَرَّ ثَلَاثٌ لَقِيَهُ فَسَلَّمَ عَلَيْهِ فَإِنْ رَدَّهُ فَقَدِ اشْتَرَكَا فِي الْأَجْرِ وَإِنْ لَمْ يَرُدَّ عَلَيْهِ فَقَدْ بَرِأَ الْمُسْلِمُ مِنَ الْهِجْرَةِ وَصَارَتْ عَلَى صَاحِبِهِ

"لَا يَحِلُّ لِمُؤْمِنٍ أنْ يَهْجُرَ مُؤْمِنًا فَوْقَ ثَلاث، فَإِنْ مَرَّتْ ثَلاثٌ فَلْيَلْحَقْهُ فَلْيُسَلِّمْ عَلَيهِ، فَإِنْ رَدَّ عَلَيهِ السَّلامَ فَقْدِ اشْتَركَا في الأَجْرِ، وَإنْ لَمْ يَرُدَّ عَلَيهِ فقد بَاءَ بِالإِثْم".