The "work of the Father" referred to here has to do with fulfilling specific covenants made with the house of Israel. They include the return of the Jews to the land of their inheritance, the gathering of Israel (Isa 43:5-7), the building of a temple in Jerusalem (Isa 44:28), the promise that the Gentiles shall bring thy sons in their arms, and thy daughters shall be carried upon their shoulders (Isa 49:22). The Lord has promised Israel, I will contend with him that contendeth with thee, and I will save thy children (Isa 49:25), and Break forth into joy, sing together, ye waste places of Jerusalem: for the Lord hath comforted his people, he hath redeemed Jerusalem (Isa 52:9). Not much progress had been made in the fulfilling of these covenants before the second world war. This places the timing of the events of verse 17 in the 20th century.