zechariah 1:12 Then the angel of the LORD answered and said, O LORD of hosts, how long wilt thou not have mercy on Jerusalem and on the cities of Judah, against which thou hast had indignation these threescore and ten years? - Free Bible Online

      12. Not only does Messiah stand among His people (the "myrtles," Zec 1:8), but intercedes for them with the Father ("Lord," or "Jehovah of hosts") effectively (Zec 1:13; Heb 7:25). Compare Ps 102:13-20; Isa 62:6, 7, as to Judah's restoration in answer to prayer.
      answered and said--said in continuation of the discourse: proceeded to say.
      how long--Messiah's people pray similarly to their Head. Re 6:10, "How long," &c. Heretofore it was vain to pray, but now that the divinely appointed "threescore and ten years" (Jer 25:11; 29:10) are elapsed, it is time to pray to Thee for the fulfilment of Thy promise, seeing that Thy grace is not yet fully manifested, nor Thy promise fulfilled. God's promises are not to make us slothful, but to quicken our prayers. HENDERSON, dating the seventy years from the destruction of Jerusalem (588 B.C.), supposes two years of the seventy had yet to run (520 B.C.).

JFB.