Jesus declared this in John 17:5,
"Now, Father, glorify Me together with Yourself, with the glory which I had with You before the world was."
Either Jesus was declaring truth when He spoke these words, or He spoke error.
Those that believe Jesus is a created being will have a hard time explaining their belief when they stand before Him at the judgment seat of Christ (2 Cor 5:10).
When one denies the deity of Jesus, then one misunderstands everything else Jesus said and did.