Haggai 2: Motivation to work on rebuilding the temple

 In general, human beings are selfish. In Haggai 2 we read:

1-3 On the twenty-first day of the seventh month, the Word of God came through the prophet Haggai: “Tell Governor Zerubbabel son of Shealtiel and High Priest Joshua son of Jehozadak and all the people: ‘Is there anyone here who saw the Temple the way it used to be, all glorious? And what do you see now? Not much, right?

The prophet says that the temple is in a bad shape compared to the former temple. The Lord calls his people to work on his temple:

4-5 “‘So get to work, Zerubbabel!’—God is speaking.
“‘Get to work, Joshua son of Jehozadak—high priest!’
“‘Get to work, all you people!’—God is speaking.
“‘Yes, get to work! For I am with you.’ The God-of-the-Angel-Armies is speaking! ‘Put into action the word I covenanted with you when you left Egypt. I’m living and breathing among you right now. Don’t be timid. Don’t hold back.’

The Lord says to work on his temple, and the Lord says that He is with his people on this job. This must be a good motivation to the believer. It would be very difficult to work on something outside our own interest without believing that the Lord is present.

14 Then Haggai said, “‘So, this people is contaminated. Their nation is contaminated. Everything they do is contaminated. Whatever they do for me is contaminated.’ God says so.
15-17 “‘Think back. Before you set out to lay the first foundation stones for the rebuilding of my Temple, how did it go with you? Isn’t it true that your foot-dragging, halfhearted efforts at rebuilding the Temple of God were reflected in a sluggish, halfway return on your crops—half the grain you were used to getting, half the wine? I hit you with drought and blight and hail. Everything you were doing got hit. But it didn’t seem to faze you. You continued to ignore me.’ God’s Decree.

The prophet says that Judah is contaminated because they are selfish, caring for their own interests. This reflects on how the temple is being treated: it is not a priority for them. So, they do the temple that should be holly but it is not, it is contaminated. They can´t expect that doing the temple in this way, the would become holly because a dirt thing contaminates clean things but not vice-versa. An objection to this idea is that Jesus was not contaminated, instead, his touch was powerful to make us right.
The text continues:

18-19 “‘Now think ahead from this same date—this twenty-fourth day of the ninth month. Think ahead from when the Temple rebuilding was launched. Has anything in your fields—vine, fig tree, pomegranate, olive tree—failed to flourish? From now on you can count on a blessing.’”

In a certain date, the temple rebuilding was launched. The Lord is saying to pay attention how He will be blessing his people from that day on. Before, they had bad crops, after, they will have good crops.
Even the work that we do normally is changed when we prioritize the Lord.