بُلُوغُ الْمَرَامِ
Bulugh al-Maram 420
The Book of Prayer
وَعَنْ وَابِصَةَ بْنِ مَعْبَدٍ ]اَلْجُهَنِيِّ] - رضى الله عنه - أَنَّ رَسُولَ اَللَّهِ - صلى الله عليه وسلم -{ رَأَى رَجُلًا يُصَلِّي خَلْفَ اَلصَّفِّ وَحْدَهُ, فَأَمَرَهُ أَنْ يُعِيدَ اَلصَّلَاةَ. } رَوَاهُ أَحْمَدُ, وَأَبُو دَاوُدَ, وَاَلتِّرْمِذِيُّ وَحَسَّنَهُ, وَصَحَّحَهُ اِبْنُ حِبَّانَ . [1] .
Narrated Wabisah bin Ma'bad: Allah's Messenger (ﷺ) saw a man praying alone behind the row so he ordered him to repeat the Salat (prayer). [Reported by Ahmad, Abu Dawud and at-Tirmidhi. The latter graded it Hasan, and Ibn Hibban graded it Sahih (authentic)].
Sunnah.com reference: Book 2, Hadith 326