"It is only in the case of the Priestly Code that opinions differ widely; for it tries hard to imitate the costume of the Mosaic period, and, with whatever success, to disguise its own"

This quote by Julius Wellhausen is describing the Priestly Code, which is a set of laws and regulations found in the Hebrew Bible. The Priestly Code is thought to have actually been composed during the post-exilic duration, which is after the Babylonian exile. Wellhausen is suggesting that the Priestly Code is attempting to mimic the laws and regulations of the Mosaic duration, which is the amount of time when Moses is thought to have actually composed the Torah. He is implying that the Priestly Code is attempting to disguise its own origin and pass itself off as being from the Mosaic duration. This is why viewpoints vary commonly when it concerns the Priestly Code, as some believe it is from the Mosaic period while others believe it is from the post-exilic duration.