"Be ready for the third day.."
God is coming to meet with Israel. He calls them to sanctify themselves; that is, to prepare themselves inside and out to meet with God. He gives them two days to do this for He will meet with them on the third day.
The third day is very significant in Scripture. We see its use in a few places, most prominently in the resurrection of our Lord after His crucifixion. The third day represents the fulfillment of God's plan. On this occasion it will be the first time that God will come down to speak to His people since their deliverance from Egypt.
What does the third day mean for us? It may mean a lot of things. It may represent a special time of devotion to God. It may also reflect the ways in which we prepare ourselves daily to meet with God.
I know there are many advocates for the idea of making prayer the first thing we do when we wake up. While I may like to greet the Lord upon rising, I find that I am much more attentive if I clean myself up first.
Then there is Mass. I remember not too long ago dressing up to meet with someone of importance. I thought to myself, if I do this for people, why don't I do the same for God? I was used to wearing a polo and slacks to Mass. Now there's really nothing wrong with that. It's acceptable attire. But I wanted to look my best because I would be meeting with Jesus in the Eucharist. So I started wearing a coat and tie. I want to look my best for the Lord. I know the Lord looks on the heart and all of that. But I also know that our outside appearance often reflects the inside state of the heart. When a person dresses up, not to show off for others, but to honor the Lord, hopefully it also reflects a corresponding attention to the inner appearance as well.
This idea of the third day also brings to mind the idea of waiting. We hate to wait, but God is very fond of it. He is not in a hurry. He uses waiting to teach us many things: patience, faith, peace, and more. He does this because He loves us. He is busy making us holy, which is to say, He is fashioning us after Himself.
Perhaps you find yourself in the midst of a first or second day, awaiting the third. Use the time to sanctify yourself in preparation. Allow God to train you in the time of waiting. Be confident that the third day will come- and it will indeed be worth it all.