1 Corinthians 15:7

Then he appeared to James; then to all the apostles; and last of all as to the child untimely born, he appeared to me also.

James ... This appearance is nowhere else mentioned in the New Testament. Macknight identified this James as "James the less, author of the New Testament book of James and a brother of our Lord."[13] As the apostle James was already dead at the time of Paul's writings, it seems probable that Paul would have been referring to the other James, who was also called an apostle in a secondary sense. He presided over the church in Jerusalem, as recorded in Acts. Jerome recorded a curious legend to the effect that James had made a vow that he would neither eat nor drink until he had seen Jesus risen from the dead, and that Jesus, appearing to him, said, "My brother, eat thy bread, for the Son of man is risen from the dead."[14] Jesus' brothers did not, at first, believe in him (John 7:3).

Last of all ... does not mean that Jesus appeared to no other afterward, because he also appeared to John at a much later time (Revelation 1:16ff). It has the meaning of "last in this list which I am giving."

Untimely born ... The word here is used of an abortion and "denotes the violent and unnatural mode of Paul's call to the apostleship."[15] Although himself one of the witnesses of Christ's resurrection, Paul here dissociated himself from the Twelve as being conscious of his own unworthiness from having persecuted the church.

[13] James Macknight, Apostolical Epistles and Commentary (Grand Rapids: Baker Book House. 1969), p. 256.

[14] Jerome as quoted by Farrar, op. cit., p. 484.

[15] David Lipscomb, op. cit., p. 224.