Adam Clarke on Isaiah 55:1

Ho, every one that thirsteth - "Water," says Zimchi, "is a metaphor for the law and wisdom: as the world cannot subsist without water, so it is impossible that it can subsist without wisdom. The law is also compared to wine and milk: to wine because wine rejoiceth the heart, as it is written: 'The statutes of the Lord are right, rejoicing the heart,' Psa 19:8. It is compared also to milk, because milk is the subsistence of the child; so are the words of the law the nourishment of his soul who walks in the Divine teaching, and grows up under it."

Come, buy wine and milk - In ancient times our forefathers used what is now called the old third person singular, ending in eth, for the imperative mood. We have a fine example of His in the first verses of this chapter. I shall present them as they stand in my old MS. Bible: - Alle gee thirstinge cummeth to wateris: and gee that han not sylver, goth forth and bieth, and etith. Cummeth, bieth without silver, and without eny chaungyng, wyn and mylc. Heerith gee, heering me and etith gode thinge, and deliten schal in fattnesse your soule. Bowith in your eie and cummeth to mee, heerith and liven schal your soule. And I shall smyten with gou, everlastynge covenant, the faithful mercies of David.