Passage
For he knew him that delivered him up: on account of this he said, Ye are not all clean.
For he knew him that delivered him up: on account of this he said, Ye are not all clean.
John 13:9 Simon Peter says to him, Lord, not my feet only, but also my hands and my head.
John 13:10 Jesus says to him, He that is washed all over needs not to wash save his feet, but is wholly clean; and ye are clean, but not all.
John 13:11 For he knew him that delivered him up: on account of this he said, Ye are not all clean.
John 13:12 When therefore he had washed their feet, and taken his garments, having sat down again, he said to them, Do ye know what I have done to you?
John 13:13 Ye call me the Teacher and the Lord, and ye say well, for I am [so].
The verse centers on "knew", "delivered", "account", "said", and "clean". It is saying that the verse draws attention to "knew" and "delivered", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 10's "Jesus says to him He that is..." into verse 12's "When therefore he had washed their feet...", so "knew" and "delivered" belong inside that flow. In John context, the local focus is the identity of Jesus, new birth, eternal life, and belief and unbelief.
A plain takeaway is to answer the verse's own emphasis on "knew" and "delivered" with trust shaped by these words, not by a vague optimism outside the passage.