John Calvin Commentary Isaiah 66:11

"that ye may suck and be satisfied with the breasts of her consolations; that ye may milk out, and be delighted with the abundance of her glory." — Isaiah 66:11 (ASV)

That you may suck. This verse ought to be joined with the preceding verse; for the Prophet explains what will be the occasion of joy, namely, that the wretched and miserable condition of the Church will be changed into a happy and prosperous condition.

By the word “suck,” he makes an allusion to young infants, as if he had said, “That you may enjoy your mother with every advantage and may hang on her breasts.” Here, all believers, whatever their age, are compared by him to children, that they may remember their infirmity and be confirmed by the strength of the Lord; and therefore, this metaphor of “sucking” and “milking” ought to be carefully observed.

From the breast of her consolations. Some take the word “consolations” in an active, and others in a passive sense; but I prefer to adopt the passive signification; for he means the consolations which the Church has received, and of which he makes his children partakers. And indeed, none can be greater or more abundant, none can be more excellent, than that ground of joy; and this appears more clearly from the following clause: that you may be delighted with the brightness of her glory.