Albert Barnes on John 13:21

Trouble in spirit. See Jn 12:27. The reason of 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 with 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 would be those of other men by baseness and treason.

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

(q) "When Jesus had thus said" Mt 26:21, Mk 14:18, Lk 22:21