Pulling someone from the last row to have at least two people in a row when joining a congregational prayer
The Messenger of Allah ﷺ left and there was a man praying alone behind the people. He said, "O you who are praying alone, why don't you join them and enter with them, or bring someone to stand beside you if the place becomes tight for you? Repeat your prayer, for indeed, there is no prayer for you."
انْصَرَفَ رَسُولُ اللهِ ﷺ وَرَجُلٌ يُصَلِّي خَلْفَ الْقَوْمِ وَحْدَهُ فَقَالَ «أَيُّهَا الْمُصَلِّي وَحْدَهُ أَلَا تَكُونَ وَصَلْتَ صَفًّا فَدَخَلْتَ مَعَهُمْ أَوِ اجْتَرَرْتَ رَجُلًا إِلَيْكَ إِنْ ضَاقَ بِكَ الْمَكَانُ أَعِدْ صَلَاتَكَ فَإِنَّهُ لَا صَلَاةَ لَكَ»