Albert Barnes Commentary John 13:28-29

"Now no man at the table knew for what intent he spake this unto him. For some thought, because Judas had the bag, that Jesus said unto him, Buy what things we have need of for the feast; or, that he should give something to the poor." — John 13:28-29 (ASV)

No man at the table knew. This shows that Jesus had signified to John only who it was that would betray him.

The bag. The traveling bag in which they put their common property. See Barnes on John 12:6.

Have need of against the feast. The feast continued seven days, and they supposed that Jesus had directed him to make preparation for their needs on those days.