A.T. Robertson Commentary Romans 2:21

"thou therefore that teachest another, teachest thou not thyself? thou that preachest a man should not steal, dost thou steal?" — Romans 2:21 (ASV)

Thou therefore that teachest another (ο ουν διδασκων ετερον). Paul suddenly breaks off (anacoluthon) the long sentence that began in verse 17 and starts over again with a phrase that gathers it all up in small compass (teachest) and drives it home (therefore) on the Jew (thyself).

Not to steal (μη κλεπτειν). Infinitive with μη in indirect command (indirect discourse) after κερυσσων.

Dost thou steal? (κλεπτεισ?). The preaching (κερυσσων) was fine, but the practice? A home-thrust.

Should not commit adultery (μη μοιχευειν). Infinitive in direct command again after λεγων. "The Talmud charges the crime of adultery upon the three most illustrious Rabbins" (Vincent).