For finding fault with them, he saith, Behold, the days come, saith the Lord, when I will make a new covenant with the house of Israel and with the house of Judah:
Finding fault with them - the people of the old covenant not made "faultless" by it (Hebrews 8:7); whose disregard of God's covenant made Him to 'regard them not' (Hebrews 8:9). The law is not in itself blamed, but the people who observed it not.
He saith (Jeremiah 31:31-34: cf. Ezekiel 11:19; Ezekiel 36:25-27). At Rama, the headquarters of Nebuzaradan, where the captives of Jerusalem had been led, Jeremiah uttered this prophecy of Israel's restoration under another David, whereby Rachel, wailing for her lost children, shall be comforted: in part fulfilled at the restoration under Zerubbabel: more fully to be hereafter at Israel's return to their own land; spiritually fulfilled in the Gospel, whereby God forgives absolutely His people's sins and writes His law, by His Spirit, on the hearts of believers-the true Israel. 'This prophecy forms the third part of the third trilogy of the three great trilogies into which Jeremiah's prophecies may be divided: Jeremiah 21:1-14; Jeremiah 22:1-30; Jeremiah 23:1-40; Jeremiah 24:1-10; Jeremiah 25:1-38, against the shepherds of the people; Jeremiah 26:1-24; Jeremiah 27:1-22; Jeremiah 28:1-17; Jeremiah 29:1-32, against the false prophets; Jeremiah 30:1-24; Jeremiah 31:1-40, the book of restoration' (Delitzsch in Alford).
Behold, the days come - the formula introducing a Messianic prophecy.
Make, х suntelesoo (G4931)] - 'perfect,' 'consummate.' Appropriate to the new covenant which perfected what the old could not (cf. end of Hebrews 8:9 with end of Hebrews 8:10).
Israel ... Judah - therefore, the ten tribes, as well as Judah, share in the new covenant. As both shared the exile, so both shall share the literal and spiritual restoration.