Ibn Ezra on Numbers 5:12

וטעם תשטה. בעבור ומעלה בו מעל: The portion dealing with a straying wife follows²⁹The portion that deals with one who trespasses against the Lord. because the straying wife commits a trespass against her husband.³⁰They are thus thematically connected.

תשטה. תסור מהדרך הישרה וכן שטה מעליו ועבור: IF ANY MAN’S WIFE GO ASIDE. Tisteh means will go aside from the right way.³¹In other words, the word tisteh means to go aside. Here, to go aside from the right path. Similarly seteh (go aside) in Go aside from it (Prov. 4:15).