New Defender's Study Bible Notes
4:3 yokefellow. Since this “yokefellow” is not named, it may well be that this was actually the proper name (Greek Suzugos) of a man in the church who lived up to his name.
4:3 book of life. On the “book of life,” in which God has inscribed the names of all His redeemed ones, see especially the note on Revelation 3:5.