“And Aaron shall present the bull ox of the purification for sin offering, which is for himself, and shall make atonement for himself, and for his house, and shall kill the bull ox of the purification for sin offering which is for himself,”
The detail of the ‘presenting' of the bull ox is repeated from verse 6, in order to remind us what the offering is for, and then amplified into the actual offering up of it by slaughter. There is a certain repetition in the following verses in order to make quite clear precisely what happens and what its significance is. Such repetition was common in ancient writings.