Three seifim — the Shulchan Arukh announces it itself: ובו ג׳ סעיפים. The first two do not belong to the laws of idolatry but to the guarding of life: the crowded place, the important man, the razor, the mirror. Only the third touches on worship: the blorit and the tonsure of the priests (Shulchan Arukh, Yoreh De'ah 156 — 3 seifim)
אין מסתפרין מהעובד כוכבים אלא במקום שמצויין בני אדם
One does not have one’s hair cut by the non-Jew, except in a place where people are found. The Mehaber does not write the reason; the Tur and the Rambam do, and it has nothing of a prohibition of worship about it: שמא יהרגנו, lest he kill him.
Shulchan Arukh, Yoreh De'ah 156:1
The 4 levels of study
LEVEL 01
רמת המתחיל
Base — Beginner & Intermediate
Hebrew text of the three seifim with English translation. The crowded place and the important man, the mirror and לא ילבש גבר, the blorit and the tonsure — step by step, with the mishnah of Avodah Zarah, the gemara, Tosafot, the Rambam, the Tur, the Beit Yosef, and the Shach, the Taz and the Baer Hetev in full.
In-depth study: does the halakhah follow R. Meir or the Sages; what the mirror actually accomplishes; where the condition אם יש עמו אחר comes from; the Shach’s objection to the Derishah; and לא ילבש גבר between Tosafot and the Ran.
A master table of the three seifim clause by clause, the reflex questions, the two roles of the mirror, the five golden rules and the four classic pitfalls.
The practical halakhah according to the ש״ך, the ט״ז and the באר היטב, then contemporary cases. Note: the Admur HaZaken wrote no Shulchan Arukh on Yoreh De'ah — a level of ruling, not “Daat HaRav”; the Pitchei Teshuvah and the Nekudot HaKesef do not comment on this siman.