Is it forbidden to say 'Shema' twice, and what are the consequences?

PrayerShema

Synopsis

It is forbidden to say 'Shema' twice — whether doubling the word or repeating the first verse — as it appears like belief in two divine powers. Rishonim disagree on which form is worse. B'dieved, one has still fulfilled the obligation.

Early Acharonim
Late Acharonim
Lenient
Strict
Lesser cited
Major authority

Discussion

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