Isaiah 66:10 - Matthew Poole's English Annotations on the Holy Bible

There is nothing more ordinary amongst men, than for friends and neighbours to meet together with their friends recovered from affliction, or brought into a better state, to rejoice with them, especially such friends as in their afflictions have mourned with them. Thus Mary, Luke 1:40, went to rejoice with Elisabeth, and Job's friends came to rejoice with him, Job 42:11. The prophet in like manner calls to all the friends of Jerusalem, especially such as in the days of her affliction had mourned for her, to come and rejoice and be glad with her, upon the prospect of her better state after the Babylonish captivity; or at least in the time of the Messiah; for though joy and gladness be the affection of the soul that works upon its union with its desirable object, and the deliverance of the people out of Babylon was not to be for many years after this, nor the Messiah to come for many years after that; yet faith being the evidence of things not seen, there is a rejoicing of hope, hope giving the soul a union with its object hoped for; and these things were now present to believers, who by faith called the things that were not as if they were, because they had the security of a Divine revelation for them, and they were already existent in their necessary causes.