Mighty things - Or, as in the margin. The words are probably a quotation from Isaiah 48:6.

Call unto eve, and I will answer thee - To me alone it belongs to reveal what is future; and the stupendous things which are now coming are known only to myself. These idolaters go to their gods to get information relative to the issue of the present commotions; but there is no light in them. Ask thou, O Jeremiah, and I will tell thee the great and mighty things which even thou knowest not.

Call unto me, and I will answer thee,.... This is spoken not to Jerusalem, and the inhabitants of it; but to the prophet, encouraging him to seek the Lord by prayer, promising an answer to him. So the Targum,
"pray before me, and I will receive thy prayer:''
and show thee great and mighty things; or, "fortified ones" (p); which are like fortified cities, that cannot easily be come at, unless the gates are opened to enter into; and designs such as are difficult of understanding, which exceed human belief, and which reason cannot comprehend and take in; and such are the great things of the Gospel. Some copies read it, "things reserved" (q); as the Targum; and so Jarchi, who interprets it of things future, of things reserved in the heart of God, and which he purposed to do; and very rightly:
which thou knowest not; until revealed; and from hence it appears, that by these great and hidden things are not meant the destruction of Jerusalem, and the seventy years' captivity, and return from that, things which Jeremiah had been made acquainted with time after time, and had prophesied of them; but spiritual blessings hereafter mentioned, some of which the deliverance from Babylon were typical of Ben Melech interprets these of comforts great and strong.
(p) "munita", Vatablus, Paganinus, Montanus; "fortia", Tigurine version. (q) "abstrusa", Junius & Tremellius, Piscator; "recondita", so some in Vatablus.

Call . . . I will answer-- (Jeremiah 29:12; Psalm 91:15). Jeremiah, as the representative of the people of God, is urged by God to pray for that which God has determined to grant; namely, the restoration. God's promises are not to slacken, but to quicken the prayers of His people (Psalm 132:13, Psalm 132:17; Isaiah 62:6-7).
mighty things--Hebrew, "inaccessible things," that is, incredible, hard to man's understanding [MAURER], namely, the restoration of the Jews, an event despaired of. "Hidden," or "recondite" [PISCATOR].
thou knowest not--Yet God had revealed those things to Jeremiah, but the unbelief of the people in rejecting the grace of God had caused him to forget God's promise, as though the case of the people admitted of no remedy.