Revelation 22:17 And the Spirit and the bride say, Come. And let him that heareth say, Come. And let him that is athirst come. And whosoever will, let him take the water of life freely.
The invitation is to believe and obey the gospel in order to receive the reward of eternal life in the kingdom of God. The invitation is from the spirit of God in that it is contained in the scriptures written by inspiration.
Peter 1:21 For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Spirit.
2 Timothy 3:16 All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness: 17 That the man of God may be perfect, throughly furnished unto all good works.
The invitation is also from the bride – those men and women who have believed and obeyed the gospel and preach it.
1 Corinthians 1:21 For after that in the wisdom of God the world by wisdom knew not God, it pleased God by the foolishness of preaching to save them that believe.
Mark 16:15 And he said unto them, Go ye into all the world, and preach the gospel to every creature. 16 He that believeth and is baptized shall be saved; but he that believeth not shall be damned (condemned).
I hope you find this helpful.