'Legitimate' in the Bible

In Christ Jesus, then, I have found [legitimate] reason for boasting in things related [to my service] to God.

All things are lawful [that is, morally legitimate, permissible], but not all things are beneficial or advantageous. All things are lawful, but not all things are constructive [to character] and edifying [to spiritual life].

We, on the other hand, will not boast beyond our proper limit, but [will keep] within the limits of our commission (territory, authority) which God has granted to us as a measure, which reaches and includes even you.

We are not overstepping the limits of our province, as if we did not [legitimately] reach to you, for we were the [very] first to come even as far as you with the good news of Christ.

But if you are without discipline, in which all [legitimate sons] have become participants, then you are illegitimate and not sons.