The gathering of Israel and the Lord's fulfilling his covenants with the house of Israel are concepts so intertwined as to be inseparable. Neither can take place without the other. None of the glorious promises, many of which were given by Isaiah, can have their fulfillment without the gathering. Indeed the gathering itself was part of the covenant which was made (Deut 30:1-5). An example of the relationship between these two concepts is as follows:
'For a small moment have I forsaken thee; but with great mercies will I gather thee…
For the mountains shall depart, and the hills be removed; but my kindness shall not depart form thee, neither shall the covenant of my peace be removed, saith the Lord that hath mercy on thee…
And all thy children shall be taught of the Lord; and great shall be the peace of thy children.
In righteousness shalt thou be established.' (Isa 54:7,10,13,14)