John Gill Commentary Job 27:3

"(For my life is yet whole in me, And the spirit of God is in my nostrils);" — Job 27:3 (ASV)

All the while my breath [is] in me
So long the oath of God would be upon him, or he bound himself under it: and the spirit of God [is] in my nostrils ;
which signifies the same thing.

The breath of a man is his spirit, and this is of God, the Father of spirits; he first breathed into man the breath of life, and he became a living soul or spirit, (Genesis 2:7); it is he that gives life and breath to every man, (Acts 17:25), and continues it as long as he pleases, which is a very precarious thing; for it is in his nostrils, where it is drawn to and fro and soon and easily stopped; nor will it always continue, it will some time not be, it will go forth, and then man dies, and returns to the earth, (Ecclesiastes 12:7);

but as long as there is breath there is life; so that to say this is the same as to say, as long as I live, or have a being, (Psalms 104:33) (116:2); and while that continued, Job looked upon himself under the oath he had taken by the living God.