His bones, i.e. his whole body, even the strongest parts of it, which may seem most remote from danger. Of the sin of his youth, Heb. of his youth, i.e. of his youthful pleasures and lusts, by a metonymy of the subject. And this may be understood either,
1. Of the sins themselves, that he shall persevere in his youthful lusts even in old age, and shall die without repentance. Or rather,
2. Of the punishment of his sins, of which he is speaking both in the foregoing and following verses. He shall feel the sad effects of those sins in his riper years, as riotous sinners commonly do; and, as it follows, attended him to his grave. Or, with his secret ways or sins, as others render it; whereby he possibly intimates that Job, though he appeared righteous before others, yet was guilty of some secret wickedness, for which God was now reckoning with him.