(1) While that "God is the deliverer of his people" is the concept on which, virtually, the whole Salvation), yet the Hebrews seem never to have felt the need of a title for God that would sum up this aspect of His relation to man. Nearest to our word "Saviour" is a participial form (moshia`) from the verb yasha` (Qal not used; "save" in Hiphil), but even this participle is not frequently applied to God (some 13 times of which 7 are in Isa 43:1-63:19).
(2) In the Lu 1:47; 2:11; Ac 5:31; 13:23; Eph 5:23; Php 3:20. And there are no occurrences in Matthew, Mark, or the earlier . The data are clear enough. As might be expected, the fact that the Old Testament used no technical word for Saviour meant that neither did the earliest Christianity use any such word. Doubtless for our Lord "Messiah" was felt to convey the meaning. But in Greek-speaking Christianity, "Christ," the translation of Messiah, soon became treated as a proper name, and a new word was needed.
(3) Soter expressed the exact meaning and had already been set apart in the language of the day as a religious term, having become one of the most popular divine titles in use. Indeed, it was felt to be a most inappropriate word to apply to a human being. Cicero, for instance, arraigns Verres for using it: "Soter .... How much does this imply? So much that it cannot be expressed in one word in Latin" (Verr. ii.2, 63, 154). So the adoption of Soter by Christianity was most natural, the word seemed ready-made.
(4) That the New Testament writers derived the word from its contemporary use is shown, besides, by its occurrence in combination with such terms as "manifestation" (epiphaneia, 2Ti 1:10; Tit 2:13), "love toward man" (philanthropia, Tit 3:4), "captain" (archegos, Ac 5:31; compare Heb 2:10), etc. These terms are found in the Greek sources many times in exactly the same combinations with Sorer.
(5) In the New Testament Soter is uniformly reserved for Christ, except in Lu 1:47; Jude 1:25, and the Pastorals. In 1Ti 1:1; 2:3; 4:10 it is applied only to the Father, in 2Ti 1:10, (only) it is applied to Christ, while in Titus there seems to be a deliberate alternation: of the Father in 1:3; 2:10; 3:4; of Christ in 1:4; 2:13; 3:6.
P. Wendland, "Soter" Zeitschrift fur neutestamentliche Wissenschaft, V, 335-353, 1904; J. Weiss, "Heiland," in RGG, II, 1910; H. Lietzmann, Der Weltheiland, 1909. Much detailed information is available in various parts of Deissmann, Light from the Ancient East, 1910.