Leviticus 18:14

So, again, with the wife of the father's brother, because the nakedness of the uncle was thereby uncovered. The threat held out in Lev 20:19 and Lev 20:20 against the alliances prohibited in Lev 18:12-14, is that the persons concerned should bear their iniquity or sin, i.e., should suffer punishment in consequence (see at Lev 5:1); and in the last case it is stated that they should die childless. From this it is obvious that sexual connection with the sister of either father or mother was not to be punished with death by the magistrate, but would be punished with disease by God Himself.

Here is, I. A general law against all conformity to the corrupt usages of the heathen (Lev 18:1-5). II. Particular laws, 1. Against incest (Lev 18:6-18). 2. Against beastly lusts, and barbarous idolatries (Lev 18:19-23). III. The enforcement of these laws from the ruin of the Canaanites (Lev 18:24-30).

18:14 Having sexual relations with your aunt would dishonor your uncle. In turn, this would also dishonor your father (see 20:20).