Why does the Torah not mention the Semichah?
Ramban: Semichah was mentioned earlier regarding all the Chata'os and the Korbanos Nedavah in the Parshah (it did not need to mention it here). 1
Ramban: The Torah inverted the order. First he brings the Korban, then leans on it and confesses, like we find below (16:21).
The Torah calls his Korban "Ashamo", and afterwards "l'Chatas"!
Ramban (15), Moshav Zekenim: "Ashamo" means 'his Korban'. It is a Chatas, for it is a female.