Charles Ellicott Commentary Leviticus 18:3

"After the doings of the land of Egypt, wherein ye dwelt, shall ye not do: and after the doings of the land of Canaan, whither I bring you, shall ye not do; neither shall ye walk in their statutes." — Leviticus 18:3 (ASV)

After the doings of the land of Egypt. —During their stay in Egypt, the Israelites became familiar with the practices that prevailed in the land of their bondage. Since they adopted some of them , they are here solemnly warned to avoid those that are especially forbidden in what follows.

And after the doings of the land of Canaan. The danger of imitating the customs they had witnessed for centuries in the land they left was greatly increased because these licentious practices existed in worse forms in the land they were to inherit. It is therefore against the past and the future that they are warned here.

Neither shall you walk in their ordinances. Since some of “the doings” referred to may have been simple custom, not based upon the law of the country where they prevailed, the Lawgiver here emphatically condemns the acts that were legalized, declaring them to have no authority whatever. (See Leviticus 18:30.)