Haggai's next prophecy comes on the 24th day of 9th month (3 months on from 1:14,15). Presumably those months were full of activity on the temple. They have received the Lord's encouragement to work and there is every reason to think they did work.
So what will the Lord say to his people now? The message is slightly unusual and begins with 2 questions to the Priests:
1) Does something become holy (consecrated) by contact with that which is holy? Answer: No.
2) Does something become defiled by contact with that which is defiled? Answer: Yes
Why ask these questions? The Lord has something to say about the people and the nation: whatever they do or offer is defiled. Therefore, they themselves must be defiled. They are unholy. They don't become holy by their contact with a holy place (the temple). Rather, they make what they do & what they offer there unholy because of their defilement.
So what will come next? Condemnation? Judgement? Exile?
In vv.15-17, the Lord reminds them how things were before. They knew his displeasure and yet did not turn to him. Will it happen again? They must give careful thought to the situation. Look around says the Lord and see: you still haven't any evidence of blessing. But "from this day on I will bless you".
Perhaps expecting rebuke, they receive a promise of blessing! What can explain this? They have done what they failed to do before: they have turned to the Lord. They have repented. There has been a decisive change in their lives. They once again reverence the Lord and are hard at work for him.
Has that merited the blessing of the Lord? The question & answer session with the priests seems designed to remind the people of their sinfulness, of their uncleaness. They can never merit the blessing of God.
So why is the Lord promising to bless them? Sheer grace! Their turning has not merited blessing but the Lord will meet them with his blessing. The last 2 months have presumably shown their repentance to be real. But they need to know that when blessing comes, it isn't down to works; it is all of grace. Remember the Prodigal Son! Utterly unworthy yet blessed greatly.
How much we need to grasp this for ourselves! We begin the Christian life through grace and we continue by grace. There is never a moment when we can say 'We deserve the blessing of God'. We are sinners still; saved yes but still unworthy and wretched.
How great then is the grace of God! How much this message must have motivated & strengthened the people in their work. The Lord loves them and is with them, despite their failures.
If anything is accomplished through our lives & ministries, it is not by virtue of any holiness or power of ours. The credit belongs entirely to the Lord and is a product of his amazing grace. See how Peter responds to the people when the man is healed at the Beautfiul Gate; Acts 3:11ff. Do we share that conviction? We need to.
This passage should stregthen our resolve to repent, to turn again to the Lord as & when we need to do so. It also reminds us that our turning is not meritorious; all is of grace. If a temple is raised up, it will be by grace and fully to the glory of God!