Acts 20:28, Overseers, to shepherd the church.

The word bishop is the Greek word ἐπίσκοπος (pronounced episkopos) and means “an overseer, patron, one who watches or protects, one who cares for others, a man charged with the duty of seeing that things to be done by others are done rightly, any curator, guardian or superintendent; the superintendent, elder, or overseer of a Christian church” (TDNT, vol. 2, p. 608). This word or related cognates occur only several times in the NT (Luke 19:44; Acts 1:20; 1 Tim 3:1, 2; 2 Tim 4:22; Tit 1:7; 3:15; 1 Pet 2:12, 25). 

Yeshua is the Chief Shepherd and Bishop over his people (1 Pet 2:25), with those holding those earthly offices under his authority. 

The TDNT notes that the role of the episkopos is to strengthen that of the pastor in watching over the flock (e.g. Acts 20:28; 1 Pet 5:2). The NT with regard to the congregation in Ephesus seems to equates the episkopos with the presbuteros (or elders-leaders of a congregation, see Acts 20:28) indicating that there is more than one leader or overseer over a congregation—literally, a group of leader-elders. Elders (presbuteros), pastors (poimen) and bishops (episkopos) are again viewed as equivalent in regards to local leadership in 1 Peter 5:1 and 2. In this passage, the leadership terms are in the plural, thus not indicating a central lead figure per se although it is the scriptural norm from the time of the patriarchs, through the priesthood, judges and kings of Israel to have a human who exercises ultimate authority. Such leaders can be elected (Acts 1:21ff; 6:3ff) or be appointed by an apostle (Acts 14:23; ibid., p. 615f).