Exodus 23 does re-mention the Sabbath, but it has far more to say about "living the Law". 

We're struck in this chapter by how strongly Sabbath is connected to broader ideas of justice. God seems highly focused on the plight of the poor and the foreigner, and the Sabbath is to be a blessing for them as much as it is for the blessed and wealthy. There are challenges here for anyone wishing to be a Sabbath-keeper.