Ambassador - (Easton's Bible Dictionary)
In the Old Testament the Hebrew word tsir, meaning "one who goes on an errand," is rendered thus (Josh. 9:4; Prov. 13:17; Isa. 18:2; Jer. 49:14; Obad. 1:1). This is also the rendering of melits, meaning "an interpreter," in 2 Chr. 32:31; and of malak, a "messenger," in 2 Chr. 35:21; Isa. 30:4; 33:7; Ezek. 17:15. This is the name used by the apostle as designating those who are appointed by God to declare his will (2 Cor. 5:20; Eph. 6:20).
The Hebrews on various occasions and for various purposes had recourse to the services of ambassadors, e.g., to contract alliances (Josh. 9:4), to solicit favours (Num. 20:14), to remonstrate when wrong was done (Judg. 11:12), to condole with a young king on the death of his father (2 Sam. 10:2), and to congratulate a king on his accession to the throne (1 Kings 5:1).
To do injury to an ambassador was to insult the king who sent him (2 Sam. 10:5).