Position of a single follower standing to the Imam's left
Chapter on Imamate and Congregational Prayer
Al-Mughni
Book of Prayer
Primary text
If a single follower stands to the Imam's left, his prayer is valid if there is someone else on the Imam's right, following the action of Ibn Mas'ud who prayed between 'Alqamah and Al-Aswad. This is also because the space to the Imam's left is a valid standing position for women and the uncovered. However, if there is no one to the Imam's right, the prayer of one standing to his left is invalid, whether he is alone or with others.
Supporting text
Most scholars hold that the single follower should stand to the Imam's right, and standing to the left opposes the Sunnah. Sa'id ibn Al-Musayyib is reported to have placed a single follower on his left. Malik, Al-Shafi'i, and the proponents of opinion hold that if he stands to the left, his prayer is valid, citing the Prophet moving Ibn 'Abbas from his left to his right without invalidating his *takbir*.