'Son of Man' in the Bible

What is man, that thou art mindful of him? and the son of man, that thou visitest him?

Let thy hand be upon the man of thy right hand, upon the son of man whom thou madest strong for thyself.

LORD, what is man, that thou takest knowledge of him! or the son of man, that thou makest account of him!

Put not your trust in princes, nor in the son of man, in whom there is no help.