'Of the Flesh' in the Bible

You know how through weakness of the flesh I preached the gospel unto you at the first.

This I say then, Walk in the Spirit, and you shall not fulfill the lust of the flesh.

Now the works of the flesh are manifest, which are these; Adultery, fornication, impurity, licentiousness,

For he that sows to his flesh shall of the flesh reap corruption; but he that sows to the Spirit shall of the Spirit reap life everlasting.