I am trying to figure out when several parshiyos in Vayikra were said by Moshe to bnei yisroel. For example, the parshiyos of Tazria and Metzora - when did Moshe teach them? In במדבר פרק ה Hashem commands Moshe to send all the טמאים out of the מחנות. Included in this command are the מצורעים. Rashi, quoting the gemara in .גיטין דף ס, tells us that this is one of the 8 parshiyos that were taught on Rosh Chodesh Nissan. So how did anyone or the Kohanim know the laws of Tazria and Metzora in order to send out or be sent out, if they weren’t taught yet. To further explain, we know that from the end of parashas פקודי through פרק ז in sefer Vayikra, Hashem is teaching the laws of קרבנות to Moshe and this is taking place on Rosh Chodesh Nissan(according to Rashi). Then פרק ח jumps briefly back to 23 Adar and then פרק ט which is parashas Shemini is back to Rosh Chodesh Nissan. פרק י is Nadav and Avihu bringing the korban and being killed, also on Rosh Chodesh Nissan. Then פרק יא teaches the laws of kashrus. Was this also on rosh chodesh nissan? The gemara in גיטין doesn’t mention it as one of the 8 parshiyos said on that day. Then comes Tazria and Metzora. When did Moshe teach these laws?