Romans 11:23,24

“ And they also, if they abide not still in unbelief, shall be grafted in; for God is able to graft them in again. For if thou wert cut out of the olive tree which is wild by nature, and wert grafted contrary to nature into a good olive tree, how much more shall these, which be the natural branches, be grafted into their own olive tree! ”

Severity to the Jews was a threat to the Gentiles; so the goodness displayed to the Gentiles is a pledge, as it were, of mercy to the Jews. Let them only give up persisting in their unbelief (a contrast to the non-persistence of the Gentiles in faith, Romans 11:22), and on this one condition the power of God will restore them their place in His kingdom. It will engraft them on Christ, who will become to them a vivifying stem, as well as to the Gentiles. And this transplantation will be effected more easily still in their case than in the case of the Gentiles.