The Prophet ﷺ said, "It is not lawful for a Muslim to desert (not to speak to) his brother Muslim for more than three days while meeting, one turns his face to one side and the other turns his face to the other side. Lo! The better of the two is the one who starts greeting the other."
عَنِ النَّبِيِّ ﷺ قَالَ لاَ يَحِلُّ لِمُسْلِمٍ أَنْ يَهْجُرَ أَخَاهُ فَوْقَ ثَلاَثٍ يَلْتَقِيَانِ فَيَصُدُّ هَذَا وَيَصُدُّ هَذَا وَخَيْرُهُمَا الَّذِي يَبْدَأُ بِالسَّلاَمِ وَذَكَرَ سُفْيَانُ أَنَّهُ سَمِعَهُ مِنْهُ ثَلاَثَ مَرَّاتٍ