Here the two manuscripts read “ye shall be cut off from his presence”. The 1830 typesetter accidentally replaced cut with cast. The 1981 LDS edition, following the manuscripts, restored the original cut. Here Alma is talking with Shiblon (his second son). Earlier in his discourse with Helaman (his first son), Alma twice used these same words: “ye shall be cut off from his presence” (Alma 36:30 and Alma 37:13). Overall in the original text, there are 21 occurrences of “to be cut off from God’s presence” but only two of “to be cast off from God’s presence” (1 Nephi 8:36 and Helaman 12:25). So either reading is possible, although cut is considerably more frequent. For a general discussion of the competition between cut and cast, see under 2 Nephi 30:2.
Summary: Maintain in Alma 38:1 the use of cut rather than cast in “ye shall be cut off from his presence”, the reading of both manuscripts and the more frequent reading in the text.