Albert Barnes Commentary John 6:38

"For I am come down from heaven, not to do mine own will, but the will of him that sent me." — John 6:38 (ASV)

For I came down, etc. This verse shows that he came for a specific purpose, which he states in the next verse, and means that, as he came to do his Father's will, he would be faithful to the trust. Though his hearers should reject him, yet the will of God would be accomplished in the salvation of some who should come to him.

Mine own will. See Barnes on John 5:30.