The mission of God as seen in the Ten Commandments: As God set Israel free from slavery, He wanted to frame their public and private lives by introducing how relationship with Him and with others was to look like – you will only have one God, you will not have idols, you will not take His name in vain…. You will not murder, steal, commit adultery, want what is someone elses…

And as Israel would obey these commands in their (to use the words of Newbigin) public and private lives, they would be a light for the nations.
And so the Ten Commandments reflect the missional heart of God in the OT – the mission of God.