"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."
"أَيُّهَا الْمُصَلِّي وَحْدَه أَلَا وَصَلتَ إِلَى الصَّفِّ فَدَخَلتَ مَعَهُمْ، أَو جَرَرْتَ إِلَيكَ رَجُلًا إِن ضَاقَ بِك الْمَكَانُ فَقَامَ مَعَكَ أَعِدْ صَلاتَكَ فإنَّهُ لَا صَلاة لَكَ ".
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»
"When one of you encounters a complete row, let him call a man to stand next to him."
"إِذَا انْتهَى أحدُكم إلى الصّفِّ وقدْ تَمَّ فْليجذْب إليه رَجُلًا يُقيمه إلى جنْبِه".