Does the one who is substituted in the prayer start from the beginning?

Question:
Does the substitute repeat the prayer from the beginning?

Answer:
No, he completes it with them; he completes what remains, just as 'Abd al-Rahman completed with the people what remained of 'Umar's prayer. This is the correct view. If he repeats it from the beginning, it is valid. Some scholars hold that he should repeat it from the beginning, so if he holds this opinion, there is no harm; if he repeats it from the beginning, there is no blame, but it is better that he complete it with them.