The Lord declared to Moses that if Israel obeyed Him, He would make them become a kingdom of priests, and a holy nation.
“So Moses came and called for the elders of the people, and laid before them all these words which the LORD commanded him. Then all the people answered together and said, ‘All that the LORD has spoken we will do.’ So Moses brought back the words of the people to the LORD” (Exodus 19:7-8).
The Lord made a commitment to Israel and Israel then made a commitment to the Lord. Their commitment meant something and so Moses brought their word back to the Lord. Later they would be tested to see whether they would keep that commitment or not, just as we are tested to see whether we will remain loyal to the Lord during all the issues of life that we face.