Zechariah - The Prophet of the day of the Lord

Zechariah encourages the exiles, who had returned to Jerusalem but were struggling with endless disappointments, not to despise the ‘day of small things’ but to look forward to the day of Yahweh when God will bring in his kingdom.

How does Zechariah encourage us that what we do for God, even though it may seem small, has eternal consequences and that in the kingdom our labour is never in vain?