The One Lord

Jesus has all Authority in Heaven and on Earth.

Then Jesus came to them and
said, "All authority
in heaven and on earth has been given to me. Mt 28:18

The only other position open in the Kingdom is that of Follower / Disciple

There is only One Lord but an unlimited number of disciples. Man sometimes forgets who is the Lord and who is the disciple, however, so Jesus gave some clear definition to our responsibilities as disciples.

To the Jews who had believed him, Jesus said, "If you
hold to my teaching, you are really my disciples"... Jn 8:31

"By this all men will know that you are my
disciples, if you love one another." Jn 13:35

"This is to my Father's glory, that you bear much fruit,
showing yourselves to be my disciples." Jn 15:8

Is agreement on the One Lord
essential for salvation / unity?

YES / NO