Hebrews 4:13

And there is no creature that is not manifest in his sight; but all things are naked and laid open before the eyes of him with whom we have to do.

Macknight sees in the words here a reference:

to the state in which the sacrifices called burnt offerings were laid on the altar. They were stripped of their skins, their breasts were ripped open, their bowels were taken out, and their backbone was cleft. This is the import of the original word. Then they were divided into quarters; so that outwardly and inwardly they were fully exposed to the eye of the priest, in order to a thorough examination (Leviticus 1:5,6); and, being found without blemish, they were laid in their natural order upon the altar and burnt.[9]

Here then is the explanation of the image in the author's mind that caused him to mention such things as joints and marrow, the significant warning to Christians lying in the fact that the word of God is able to discover blemishes or taints of character by means of the most thorough and accurate discernment of the entire man, such being the spiritual equivalent of the priest's minute examination of the ancient sacrifices. Not one little sin shall ever be able to crawl by the eyes of the Eternal God without receiving its just condemnation and punishment; and that is the overwhelming reason why every man should fly to Christ for refuge and forgiveness. These words of Hebrews 4:13 conclude the second great admonition of the Book of Hebrews.