I love this verse. Let me set it up for you. The verses just before said that God planned for Zerubbabel to rebuild the His temple. God was not going to let anything to get in Zerubbabel's way not even mighty mountains. God said it would not be by force of strength by by God's spirit that the temple would be rebuilt. The importance the words in verse 4:10 is that once Zerubbabel picked up the plumb line he was accepting what God ask him to do. It says that he knew that God was asking him to do something for God. He knew that God would make him able to finish what he was willing to start.
What does this say to us in our world today? It says that when God ask us to do something, God will make us able!! It is up to us to start the task to show our willingness, then God helps us with the rest... we don't need force or strength... we just need the Spirit of God.
I remember the first time I prayed with a complete stranger. I was terrified! I was in Hobby Lobby and got to talking to this lady. Her mom was dieing...she had said something to her daughter the day before about being ready to go home. We talked for a few minutes and I felt inside that I needed to say a prayer not for this lady but with her. My heart was pounding, what if my prayer did not have the right words in it? Would I say something wrong? My prayers are not elegant, they are pretty basic and rough around the edges. But I ask anyway... the lady said, "Please do!" I took her hands and in the isle of Hobby Lobby I sent up a very simple, but elegant prayer. I was surprised at the words!! You see I had to be willing but the Spirit took over.. it wasn't my words it was the Spirit of God who spoke through me that day, because I was willing. When I finished the lady had tears in her eyes and we hugged. She said to me, "You have no idea how much I needed that today, God sent you to me."
When I read this verse... "...for the Lord rejoices to see the work begin..." I realize that God rejoiced that day I was in Hobby Lobby the minute I said, "Can I say a prayer for you?" Then God took over my words. Each time we are willing to do what God prompts us to do He rejoices, then He makes us able.
I didn't build a temple that day...what I did was so tiny in comparison but it was what God ask me to do. Anything that God ask us to do is important. We may never know how important it is...but it matters. And we we act on what God says He rejoices!