zechariah 8:9 Thus saith the LORD of hosts; Let your hands be strong, ye that hear in these days these words by the mouth of the prophets, which were in the day that the foundation of the house of the LORD of hosts was laid, that the temple might be built. - Free Bible Online

      9-13. All adversities formerly attended them when neglecting to build the temple: but now God promises all blessings, as an encouragement to energy in the work.
      hands . . . strong--be of courageous mind (2Sa 16:21), not merely in building, but in general, as having such bright prospects (Zec 8:13, &c.).
      these days--the time that had elapsed between the prophet's having spoken "these words" and the time (Zec 8:10; compare Hag 2:15-19) when they set about in earnest restoring the temple.
      the prophets--Haggai and Zechariah himself (Ezr 5:1, 2). The same prophets who promised prosperity at the foundation of the temple, now promised still greater blessings hereafter.

JFB.