In the second stage of preparation, the people received commands that helped them get ready for God’s covenant.
First, they had to wash their clothing (19:10, 14). This act showed that God is pure.
Second, they had to set up a boundary around the mountain and not cross it (19:12–13). This command showed that God is holy (completely set apart).
Third, they had to abstain from sexual relations (19:15). This instruction reminded them that God is not a sexual being and that his blessings do not come from sexual activity.
These actions were not sinful in themselves. Under normal conditions, they were good and natural. However, the people had to set them aside for a special purpose.
They needed to focus completely on the Lord, their King, who was about to appear before them.
Only their obedience to the boundary command is clearly reported (19:23). Even so, since no judgment from the Lord is recorded, it is reasonable to conclude that they obeyed the other commands as well.
Hebrews 12:18–22 compares this event at Mount Sinai with the believer’s experience at Mount Zion, which it calls “the heavenly Jerusalem.”