“An overseer must be . . . upright” (Titus 1:8 NIV, also translated as “just” or “righteous”).
The underlying adjective (dikaios), used very commonly in the (Greek) OT and in the NT, is closely related to the noun meaning “righteousness.” In the NT our term is particularly used to describe or refer to believers who, through faith in Christ, have been declared righteous, and who therefore live uprightly, within the lines prescribed by God’s Word.
This term is rendered “righteous” when used of God the Father (Ps. 145:17) or the Son (Matt. 27:19; Acts 3:14). When used of men it may refer to one’s conduct in conformity to the requirements of the Law (see 1 Tim. 1:9; Rom. 8:4).
It is possible, however, for one to outwardly appear to conform to godly standards, but not actually be born of God. Such was the case with the scribes and Pharisees, who outwardly looked to be righteous but inwardly were not (Matt. 9:11-13; 23:27-28).
While it is possible for a person to appear to be righteous, but fail to be truly pious or devout, it is not possible for one to be truly devout without also being upright. This may help to explain why the term dikaios (upright or just) is sometimes paired with the term hosios (holy or devout). Such is the case in Titus 1:8.
The elder, then, must not only be a believer (1 Tim. 3:6; Titus 1:8-9), but manifest the fruit of his justification and ongoing sanctification by righteous living in his relationship to others (James 2:14; 1 John 4:20-21).
When an elder is both upright and devout he manifests the very character of God (John 17:25, Rev. 16:5), and also follows the example of Paul (1 Thess. 2:10).