A.T. Robertson Commentary Revelation 16:15

"(Behold, I come as a thief. Blessed is he that watcheth, and keepeth his garments, lest he walked naked, and they see his shame.)" — Revelation 16:15 (ASV)

Behold, I come as a thief (ιδου ερχομα ως κλεπτης). The voice of Christ breaks in with the same metaphor as in 3:3, which see. There comes one of seven beatitudes in Rev. (1:3; 14:13; 16:15; 19:9; 20:6; 22:7,14). For γρηγορων (watching) see 3:2, and for τηρων (keeping), 1:3.

Lest he walk naked (ινα μη γυμνος περιπατη). Negative purpose clause with ινα μη and the present active subjunctive of περιπατεω, and note predicate nominative γυμνος (naked).

And they see his shame (κα βλεπωσιν την ασχημοσυνην αυτου). Continuation of the final clause with present active subjunctive of βλεπω. Ασχημοσυνην is old word (from ασχημων, indecent, 1 Corinthians 12:23), in N.T. only here and Ro 1:27, a euphemism for την αισχυνην (Revelation 3:18).