'Man's' in the Bible

Because I say to you, my brothers, that the good news of which I was the preacher is not man's.

But from those who seemed to be important (whatever they were has no weight with me: God does not take man's person into account): those who seemed to be important gave nothing new to me;

Brothers, as men would say, even a man's agreement, when it has been made certain, may not be put on one side, or have additions made to it.