Albert Barnes on Revelation 3:21

To him that overcometh. Rev 2:7.

Will I grant to sit with me in my throne. That is, they will share his honours and his triumphs. Rev 2:26-27; Rom 8:17.

Even as I also overcame. As I gained a victory over the world, and over the power of the tempter. As the reward of this, he is exalted to the throne of the universe, (Php 2:6-11) and in these honours, achieved by their great and glorious Head, all the redeemed will share.

And am set down with my Father in his throne. Php 2:6-11. That is, he has dominion over the universe. All things are put under his feet, and, in the strictest unison and with perfect harmony, he is united with the Father in administering the affairs of all worlds. The dominion of the Father is that of the Son--that of the Son is that of the Father; for they are one. Jn 5:19, Eph 1:20, seq, 1Cor 15:24,seq.

(b) "overcometh" Rev 12:11, 1Jn 5:4,5 (c) "sit" Lk 22:30 (d) "overcome" Rev 2:17