John Gill Commentary Matthew 26:22

"And they were exceeding sorrowful, and began to say unto him every one, Is it I, Lord?" — Matthew 26:22 (ASV)

And they were exceeding sorrowful
Partly that Christ should be betrayed at all, into the hands of his enemies, by whom they knew he would be ill used; and partly, that so vile an action should be done, by one from among themselves; and greatly, because they knew not, nor could not conceive, who of them could be guilty of such an horrid sin:

and began everyone of them to say unto him, Lord, is it I ?
excepting Judas, who afterwards spoke for himself. This they said, though conscious to themselves the thing had never entered into their hearts; nor had they taken any step towards it, but with their whole souls abhorred it; yet, as knowing the treachery and deceitfulness, of their hearts, which they could not trust to; and fearing lest should they be left thereunto, they might commit such a dreadful iniquity; and as desirous of being cleared by Christ from any such imputation, and even from all suspicion of anything of this kind.