He—may Allah have mercy on him—was also asked:

Is the prayer of someone who prays alone behind the row valid or not? Are the hadiths reported concerning this authentic? Regarding the imams other than the four imams who hold this view—such as Hammād ibn Abī Sulaymān, Ibn al-Mubārak, Sufyān al-Thawrī and al-Awzā'ī—a man has said of them, meaning these particular imams: “These men need not be heeded.” What ruling applies to someone who says this? Is someone who is permitted to follow scholarly authority allowed to follow these imams, just as he may follow the four imams, or not?

He replied:

Praise be to Allah. One scholarly view is that the prayer of someone who prays alone behind the row is invalid. This is because there are two hadiths concerning this from the Prophet, may Allah bless him and grant him peace: he ordered someone who prayed behind the row to repeat his prayer, and he said:

“There is no valid prayer for someone who prays alone behind the row.”

More than one leading hadith scholar has authenticated these two hadiths, and their chains of transmission are sufficient to establish them as authoritative evidence. Indeed, those who rule contrary to them rely, in many questions, on reports with weaker chains of transmission. Neither hadith contradicts established principles; rather, their content accords with what the well-known scriptural texts and established principles entail. For congregational prayer is so named