Literary: The phrase "inherit the kingdom of God" is by Paul (1 Cor 6:9-10; 1 Cor 15:50; Gal 5:21), and may provide the general structure of the "inherit the kingdom of heaven" phrase used in the Book of Mormon. However, the more logical model phrase is found in John:
John 3:5 Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God.
In John we have a much closer phrase, including the similar position of the "except" and ending with the statement that such a person cannot enter the "kingdom of God/heaven."
This general idea of tying baptism with the entrance into the kingdom of God is repeated in the Book of Mormon (Mosiah 27:25-26; 3 Nephi 11:33). In Alma, the typical emphasis is not on baptism, however, but on repentance, as in this verse (see also Alma 9:12; Alma 11:37; Alma 39:9; Alma 40:26; Alma 41:4).
This is not the conceptual division that it might appear, as repentance is an important precursor to the baptism to accept the atonement. Alma himself will note in a later chapter:
"Alma 7:14 Now I say unto you that ye must repent, and be born again; for the Spirit saith if ye are not born again ye cannot inherit the kingdom of heaven; therefore come and be baptized unto repentance, that ye may be washed from your sins…"
In this verse Alma is very clear that there is both repentance and the process of being born again that precede entering the kingdom of heaven.