Revelation 16:5

the angel of the waters
The angel who had poured forth the third bowl in the previous verse.¹

You are righteous, O Lord . . . because You have judged
The angel proclaims God’s righteousness because He has judged. God is righteous because He alone possesses the perfect balance between grace and judgment. “The LORD is righteous in all His ways, gracious in all His works” (Ps. Ps. 145:17). “Righteous are You, O LORD, and upright are Your judgments” (Ps. Ps. 119:137). Because God is not willing that any should perish, He extends His patience and grace while horrible sin continues to abound on the earth. Because God is righteous, there will come a day when He must act against sin and bring judgment. We often confuse the relative calm of our own day for meekness and mildness on the part of God. In truth, God never changes and the strength which He acts against sin at the time of the end reflects the intensity He holds even now toward that which we often have a cavalier attitude toward.

who is and who was and who is to be
Ὁ ω῍ν καὶ ὁ ἦν, καὶ ἐσόμενος [Ho ōn kai ho ēn, kai esomenos] , the one who is and the “he was,” and the one to be. This unusual construction is likely a Hebraism. For a discussion of a closely-related grammatical phrase, see commentary on Revelation 1:4. Here, the future tense participle is based on the verb ειμι [eimi] , “to be,” whereas in Revelation Rev. 1:4+ it is based on the verb ἐρχομαι [erchomai] , “to come.” There, the emphasis is on His impending arrival. Here, upon his eternality. Most other manuscripts, including the majority of those in the MT text family and the NU text, have ὁ ο῝σιος [ho hosios] , “the holy,” instead of ἐσόμενος [esomenos] , “the one to be.”

Notes

¹ No reference is intended to the angel which “went down at a certain time into the pool and stirred up the water” (John John 5:4). Nor is this meant to indicate some sort of special angel: “He is undoubtedly a creature of the order of angels, and it is interesting to note that he has a title that would indicate that he had been placed in charge of the flowing waters of earth. Here we have an angel who is master of the waters.”—Donald Grey Barnhouse, Revelation (Grand Rapids, MI: Zondervan Publishing House, 1971), 292. We disagree—the most natural meaning is merely a reference to the angel in the previous verse who poured forth the bowl upon the water. “There is some merit in the suggestion that the ‘angel of the waters’ is simply the angel of the previous verse who poured out his bowl upon ‘the waters’ (Lenski, p. 469).”—Robert H. Mounce, The Book of Revelation (Grand Rapids, MI: William B. Eerdmans Publishing Co., 1977), Rev. 16:5.