Imam Malik, may Allah have mercy on him, said that if a person prays alone and forgets the Takbir al-Tahrimah, then he should perform the prayer again from the beginning.

And Imam Malik, may Allah have mercy on him, said that if the Imam forgets the Takbir al-Tahrimah and completes the prayer, then he should repeat it, and those who prayed behind him should also repeat the prayer, even if they themselves had said the Takbir al-Tahrimah.