42 Jesus says to them, Did you never read in the scriptures: ‘A stone which the builders rejected, this became head of the corner; this happened from the Lord and it is marvellous in our eyes’? 43 Therefore, I say to you that the reign of God will be taken from you and will be given to a people making its fruit.
The comment about the stone rejected by the builders and the preceding parable are addressed to the ‘chief priests and the elders of the people’ (21:23), who question his authority to enact (through the events of his arrival in Jerusalem) the judgment and restoration of Israel. The parable is directed against the tenants of the vineyard - that is, against those who were responsible for leading and caring for the people of God. The conclusion is that the owner of the vineyard will put the tenants to death and let out the vineyard to faithful tenants who will give the fruit of the vineyard to the owner. In other words, God will destroy the corrupt leadership of Israel and entrust his people to a new leadership that will give him what is rightfully his.
As Jesus puts it in 21:43, the reign of God will be taken from the present rulers of the people and given to a people that will produce the fruit that Israel should have given to God. This people presumably is thought to consist of renewed Israel led by faithful leaders which will produce the fruit that YHWH has been looking for. The argument is very similar, in effect, to the parable of the talents (Matt. 25:14-30).
But what is the significance of the quotation in 21:42 of Psalm 118:22-23? The context presupposed by the psalm is a military victory over the nations (cf. 118:10-11). The psalmist regards this political-military ‘salvation’ as demonstration of the fact that the stone rejected by the builders has become head of the corner. The meaning is that Israel’s king has triumphed over the nations that opposed Israel, has become head above the nations (cf. Ps. 18:43). There may also be the connotation that Israel is a politically inferior nation amongst the surrounding nations, but has been given an elevated status because YHWH has fought on its behalf.
Jesus’ central argument here in his dispute with the leaders of Israel is that they will be judged and condemned for having failed in the responsibility to rule over the people in the interests of the landlord, and that this responsibility will now be given to others. By quoting Psalm 118, however, it seems likely that he is aware that this transfer of responsibility will also have implications for Israel’s position amongst the nations - that is, under Roman oppression. God will take the stone that is rejected - in the first place, Jesus himself, but also those to whom he entrusts the care of the people of God - and elevate it above the enemies of Israel. This, of course, is the story of the Son of man: the one who is rejected by his own people, who is killed by the Gentiles, will be vindicated and elevated to a position above the nations, at the right hand of God. It is through this way of suffering and death that the people will be saved from destruction.