Now on the first day of the week Mary Magdalene came to the tomb early, while it was still dark, and saw that the stone had been taken away from the tomb. So she ran and went to Simon Peter and the other disciple, the one whom Jesus loved, and said to them, “They have taken the Lord out of the tomb, and we do not know where they have laid him.” So Peter went out with the other disciple, and they were going toward the tomb. Both of them were running together, but the other disciple outran Peter and reached the tomb first. And stooping to look in, he saw the linen cloths lying there, but he did not go in. Then Simon Peter came, following him, and went into the tomb. He saw the linen cloths lying there, and the face cloth, which had been on Jesus' head, not lying with the linen cloths but folded up in a place by itself. Then the other disciple, who had reached the tomb first, also went in, and he saw and believed; for as yet they did not understand the Scripture, that he must rise from the dead. Then the disciples went back to their homes. (Jn 20:1-10)
There are various reasons for believing that John is “the other disciple”, who beats Peter to the tomb. It had to be an emotionally taxing morning. The whole weekend. Seeing your friend die. Then going into hiding thinking they could be coming for you any moment now. What must have that been like? Then to hear the reports of the women. He isn’t there. They have taken him and we know not where.
The disciples take off running to the tomb to confirm the report. They find it empty. John doesn’t go in. He hesitates outside. It is open. Peter runs in. And John follows afterward. It says that he saw and believed. At least in this case seeing is believing. But the text doesn’t say what it was he believed. Whatever it was he kept it to himself. In any case, the linens folded up would indicate to anyone that this wasn’t a matter of grave robbery. They didn’t just “steal” the corpse. A person stealing a corpse wouldn’t bother removing the burial clothes and folding them. As yet they did not understand that he must rise from the dead. They went back to their homes. They would be in for a joyful if fearful surprise soon enough.