The manner of the prayer of fear in a four-rak'ah prayer

Question:
Honorable Shaykh, may Allah grant you success. He says: If the prayer is more than two rak'ahs, such as the four-rak'ah prayer, how is the manner of the prayer of fear in that case?

Answer:
He prays two rak'ahs with a group, and they conclude the prayer and leave. Then the other group comes, and he prays the remaining two rak'ahs with them. Thus, it is complete for the imam and shortened for the followers. The Messenger (peace and blessings be upon him) did this, and this is one of the forms of the prayer of fear: he prayed two rak'ahs with a group and concluded the prayer with them, then he prayed two rak'ahs with another group and concluded the prayer with them. The second two rak'ahs are voluntary for the Messenger (peace and blessings be upon him), while they are praying the obligatory prayer. This indicates the permissibility of praying the obligatory prayer behind a voluntary prayer.