When Jesus Christ reaps, after the tribulation when there are no longer any Believers alive on earth
(Matt 24:29), He is gathering the elect.
The apostle Paul, writing to the church of Corinth and Thessalonica, provides additional
information of this reaping but with a view towards Believers
(1 Cor 15:51; 1 Thess 4:16-18).
Since the resurrection of Believers occurs later
(Rev 20:4), "the perishable must clothe itself with the
imperishable" may refer to the white robes, which the martyrs received earlier
(Rev 6:11), in preparation of the Wedding Feast
When the angel reaps, the "grapes" are tossed into the great wine press of the wrath of God
(Rev 19:17-20), and it is Jesus Christ, when He arrives at
Armageddon, who treads on the "grapes" in this wine press (Rev 19:15).
Taken into consideration, this reaping includes the dispensation of the bowl judgments and the battle of Armageddon.
For deeper study:
What and When is the Tribulation?