The World Federation One Stop Fiqh

Ruling 1398

If after the imam says takbīrat al‐iḥrām those standing in the front row are ready to perform the prayer and are close to saying their takbīrat al‐iḥrām, then someone standing in the next row can say his takbīrat al‐iḥrām. However, the recommended precaution is that he should wait until those in the front row have completed their takbīrat al‐iḥrām.