A little later the circles represented by Matthew and Luke added to this the more popular expectation of the restored monarchy of the house of David; but the original stamp was never lost, and the functions of the Christian Messiah, as apart from his name, were always those of the Man of Enoch, much more than those of the Davidic king of the Psalms of Solomon. Finally, the concept of the Man who was to judge the world was extensively modified by the actual course of the passion, death, and resurrection of Jesus, and the Lukan writings, though probably not Mark, Q, or even Matthew, facilitated or confirmed this process by connecting the story of Jesus with the picture given in the fifty-third chapter of Isaiah of the suffering of the righteous Servant of the Lord. The Servant is a comparatively common title in the Old Testament for those who faithfully carried {53} out the will of God; it is used of Abraham, David, and Job among the sons of Israel, of Cyrus among the heathen, of Israel in general, and of the righteous portion of Israel in particular. In some parts, but not in all, the suffering of the Servant, whoever he may be, is emphasised; but there is no trace in the Old Testament, or in the later Jewish writings, that these descriptions were regarded as predictive of the future. It was inevitable that the resemblance of the death of Jesus to Isaiah liii. should sooner or later strike Christian readers of the Old Testament, but it does not appear to have done so immediately, and it is doubtful whether Isaiah liii. was the first "suffering" passage in the Old Testament to be ascribed to him. It is more probable that the use of the twenty-second Psalm was earlier. One further title of Jesus in the early Christian literature remains to be discussed. He is referred to as Son of God. What would this phrase mean in Jewish ears? In general the Jews regarded God as unique. The idea of a Son of God in any physical sense, such as seemed natural enough to the heathen world, would have been unthinkable to them, but they believed that God himself had used the phrase metaphorically to describe the relation between him and his chosen people. It was a moral sonship, not a physical one in the heathen sense, or a metaphysical one in the later Christian sense. In the later literature the phrase developed on two {54} separate lines. There was the tendency, exemplified in some of the Psalms, and still more in the Psalms of Solomon, to use the phrase "Son of God" to describe the Davidic king, but it was also used in quite a different sense in the Wisdom Literature as the description of the righteous man, and especially of the righteous man who suffered.