Mormon is alluding to 3 Nephi 14:11: “If ye then, being evil, know how to give good gifts unto your children, how much more shall your Father who is in heaven give good things to them that ask him?” The connection is obvious, but it is not a direct quotation. Rather, Mormon is creating enough of a reference to make the source recognizable but keeping his discourse in the looser mode of a paraphrase where he can more easily shape the scriptural principles to his current purpose.