A.T. Robertson Commentary Revelation 20:1

"And I saw an angel coming down out of heaven, having the key of the abyss and a great chain in his hand." — Revelation 20:1 (ASV)

Coming down out of heaven (καταβαινοντα εκ του ουρανου). As in 10:1; 18:1.

The key of the abyss (την κλειν της αβυσσου). As in 9:1.

A great chain (αλυσιν μεγαλην). Paul wore a αλυσις (alpha privative and λυω, to loose) in Rome (2 Timothy 1:16; , as did Peter in prison in Jerusalem (Acts 12:6).

In his hand (επ την χειρα αυτου). "Upon his hand," ready for use. See επ with the genitive in 1:20.