Passage
The disciples therefore looked one upon another, doubting of whom he spoke.
The disciples therefore looked one upon another, doubting of whom he spoke.
John 13:20 Amen, amen, I say to you, he that receiveth whomsoever I send receiveth me: and he that receiveth me receiveth him that sent me.
John 13:21 When Jesus had said these things, he was troubled in spirit; and he testified, and said: Amen, amen, I say to you, one of you shall betray me.
John 13:22 The disciples therefore looked one upon another, doubting of whom he spoke.
John 13:23 Now there was leaning on Jesus' bosom one of his disciples, whom Jesus loved.
John 13:24 Simon Peter therefore beckoned to him and said to him: Who is it of whom he speaketh?
The verse centers on "disciples", "therefore", "looked", "upon", "another", "doubting", and "spoke". It is saying that the verse draws attention to "disciples" and "therefore", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 21's "When Jesus had said these things he..." into verse 23's "Now there was leaning on Jesus' bosom...", so "disciples" and "therefore" 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 "disciples" and "therefore" with trust shaped by these words, not by a vague optimism outside the passage.