The words of the Lord to Alma the Younger while in his coma/trancelike state were that he should “marvel not that all mankind, yea, men and women….must be born again…”
Alma’s terminology is familiar to us, but there are linkages in his usage that fit into the Book of Mormon doctrine of the time more tightly that they do our usual conceptions.
The first clear difference between this birth of the spirit and the events that modern Saints typically equate with being born of the spirit is that Alma’s experience follows neither baptism nor the gift of the Holy Ghost. While it is possible that Alma had received these ordinances earlier, the particular “birth” that he receives is the very specific redemption from sin (see Alma 36: 12-21 for the details of his sin/redemption contrast).
Alma the Younger’s birth by the spirit is directly related to applying the atonement of Jesus Christ to his soul. This is a new birth in that his soul is born again, new again as a small child – freed from the bonds of sin.
It is into this context that we should also place the admonition of King Benjamin:
Mosiah 5:7”And now, because of the covenant which ye have made ye shall be called the children of Christ, his sons, and his daughters; for behold, this day he hath spiritually begotten you; for ye say that your hearts are changed through faith on his name; therefore, ye are born of him and have become his sons and his daughters.”
Note that Benjamin also describes this process as being “spiritually begotten.” What Alma the Younger has just done is the make the same covenant that he had rejected. Mormon began this particular discussion of Alma the Younger with a direct reference to the Benjaminic covenant:
Mosiah 26:1 “Now it came to pass that there were many of the rising generation that could not understand the words of king Benjamin, being little children at the time he spake unto his people; and they did not believe the tradition of their fathers.”
Alma’s experience is one of making the covenant that he has previously rejected, a point apparently not lost on Mormon, who so structured the text so that Benjamin’s covenant would be the frame in which we saw Alma’s “birth.” It is important to remember that the break between chapters and 26 and 27 is modern. Mormon intended this block of text to be read together.