Because the Lord kept vigil that night to bring them out of Egypt, on this night all the Israelites are to keep vigil to honour the Lord for the generations to come.
Christian worship is our response to who God is and what God has done. It has a “Because” energising it. Not that we can ever give an adequate response in return. But with God’s help we do endeavour to respond appropriately, even with all our sinful human impediments and limitations.
This is a lovely picture of the good Shepherd of Israel keeping watch over His flock by night. I’ve heard it said that when you have a baby, you never sleep the same again – at least, not for a long time. You are always inwardly alert to hear the voice, the cry of your helpless infant.
Our Heavenly Father never sleeps at all, which means we can.
“…indeed, he who watches over Israel will neither slumber nor sleep” Psalm 121:4
“In peace I will lie down and sleep, for you alone, LORD, make me dwell in safety” Psalm 4:8