20 Then Peter, turning about, saw the disciple whom Jesus loved following; the one who had leaned on his breast at supper, and said, Lord, who is the one who betrays you?
John 21:20 Cross References - RKJNT
John 13:23-26
23 Now there was leaning on Jesus' bosom one of his disciples, whom Jesus loved.
24 Therefore Simon Peter beckoned to him, that he should ask of whom he spoke.
25 He, lying on Jesus' breast, said to him, Lord, who is it?
26 Jesus answered, It is he to whom I shall give this morsel, when I have dipped it. And when he had dipped the morsel, he gave it to Judas Iscariot, the son of Simon.
John 20:2
2 Then she ran, and came to Simon Peter, and to the other disciple, whom Jesus loved, and said to them, They have taken away the Lord out of the tomb, and we do not know where they have laid him.
John 21:7
7 Therefore the disciple whom Jesus loved said to Peter, It is the Lord. Now when Simon Peter heard that it was the Lord, he put on his outer garment, (for he was stripped for work,) and cast himself into the sea.
John 21:24
24 This is the disciple who testifies of these things, and wrote these things: and we know that his testimony is true.