The Imam waiting for the Worshippers during Bowing
Question :
Is it necessary for the Imam to wait if he hears them (the latecomers) running during bowing, or at the end of the final Tashahhud?
Answer:
It is better not to hurry; it is better for the Imam to proceed slowly, in a manner which does not cause difficulty to the believers, because consideration to those led in prayer who came first is more important. So he should defer to them. But if he delays just a little so that those arriving may catch the bowing, the prostration or the Tashahhud, it is better and preferred for the Imam to do so.
Source:
Ibn Baz
Fatawa Islamiyah, Vol. 2 Pages 325-326