His breath goeth forth, he returneth to his earth; or, "when his breath goes forth"—i.e; when he breathes his last—"he returns to his earth," i.e. to the earth of which he was made (Genesis 2:7, Genesis 2:19).
In that very day his thoughts perish. All his schemes and projects ('eshtonoth, a word not occurring elsewhere) come to an end—are nipped in the bud—perish. So weak is he, and not to be depended on.