Albert Barnes Commentary John 13:21

"When Jesus had thus said, he was troubled in the spirit, and testified, and said, Verily, verily, I say unto you, that one of you shall betray me." — John 13:21 (ASV)

Trouble in spirit. See John 12:27. The reason for his trouble here was that Judas, a professed friend, was about to betray him. He doubtless foresaw the deep and dreadful sorrows of his approaching death and was also deeply affected by the ingratitude and wickedness of a professed friend. Jesus was man as well as God, and he felt like other men. His human nature shrank from suffering, and his tender sensibilities were affected not less deeply than those of other men would be by baseness and treason.

Testified. He bore witness to the truth; openly declared what he had previously intimated—that one of them would betray him.