Jamieson, Fausset and Brown on Revelation 4:2

2. And--omitted in the two oldest manuscripts, Vulgate, Syriac.

I was, &c.--Greek, "I became in the Spirit" (see on Re 1:10): I was completely rapt in vision into the heavenly world.

was set--not was placed, but was situated, literally, "lay."

one sat on the throne--the Eternal Father: the Creator (Re 4:11): also compare Re 4:8 with Re 1:4, where also the Father is designated, "which is, and was, and is to come." When the Son, "the Lamb," is introduced, Re 5:5-9, a new song is sung which distinguishes the Sitter on the throne from the Lamb, "Thou hast redeemed us to God," and Re 5:13, "Unto Him that sitteth upon the throne, and unto the Lamb." So also in Re 5:7, as in Da 7:13, the Son of man brought before the Ancient of days is distinguished from Him. The Father in essence is invisible, but in Scripture at times is represented as assuming a visible form.