Paul in ~58, at 1 Cor 15:5, is first to tell us: “and was seen by Cephas.”

Anonymous in ~255 at Rebaptism 9: “and some of themselves, even when they had seen him, did not believe, but doubted.” Function: again, to show that error was rife even among the chosen, so Cyprian should not want to rebaptise restored heretics.

Tertullian in 207 at Adv. Marc. 4,43 reports the doubts of many caused by Marcion’s claim that Christ was not a real physical human, but perhaps only a literary construct, a spiritual entity: “He says to them, Why are you troubled, and why do doubts arise in your hearts?

Look, my hands and my feet, that it is I myself; for a spirit has not bones, as you see me have.” Function: physical detail like hands and feet are very important against Marcion.
Justin Martyr in ~160 (Resurr 9): “When his disciples (people like Marcion and the Jews) did not know whether to believe he had truly risen in the body and were looking upon him and doubting, he said to them: You don’t yet have trust, see that I am myself. And he let them handle him, and showed them the prints of the nails in his hands. And when they were by every kind of proof persuaded that it was himself, and in the body, they asked him to eat with them, that they might thus still more accurately ascertain that he had in verity risen bodily; and he ate honey-comb and fish.” Function: a description of the now alarming problem in the church in Justin’s later years: the Gnostic denial of the physical reality of Christ, among other orthodox doctrines, especially “that we possess eternal duration from the excelling power of this Being” (5,2,3).

Ignatius of Antioch ~107 (Sm 3): “Feel me and see, because I am not a demon, incorporeal.” Function: vs. the docetists (Grk “seeming”) with their idea of a “seemingly real,” but only a virtual or phantom Christ.