By faith he kept the Passover and the sprinkling of blood, lest he who destroyed the firstborn should touch them. (Hebrews 11:28, NKJV).
There is a mistaken perception that the Eternal God is a grandfatherly figure whose bark is worse than His bite. The ancient Egyptians would disagree.
Moses warned Pharaoh that the tenth of the promised plagues would be the worst, but despite the irrefutable proof of the previous nine, Pharaoh took refuge in stubborn (and fatal) denial. Sin and pride made him stupid.
The blood of the Passover Lamb (an undeniable picture of the future sacrifice of Jesus, the Lamb of God, who takes away the sin of the world) sprinkled on the lentils of the door post was all that stood between a given household and the tragic death of its firstborn during that horrible night of judgment in Egypt.
Following explicit instructions from God, His Angel of Death destroyed every single creature, man and beast, that first opened the womb, unless that household was sheltered under the blood of the sacrifice.
All it took to avoid that result was to have sufficient faith to both hear and obey the word of warning that came prior to the massacre.
The characteristically devastating judgments of God that are chronicled throughout the Old Testament are by no means abrogated by the forgiveness offered in the New.
Make no mistake. He who destroyed the firstborn then because of unbelief, will destroy all those who willfully fail to believe today. It is the same God, with the same righteous wrath against sin, and the same requirement for pardon: faith.
To relegate God to some comfortable image is perhaps worse than outright hostility. To view God through vain human imaginings is to give the creature, rather than the Creator all authority.
God neither bargains nor suffers negotiation. He will only forgive sin through faith in His Son, who took the penalty of our iniquity on Himself that we might live.
Pharaoh heard God's word through Moses again and again, hardening his heart each time until, finally, God hardened his heart against the truth. The fate of his household and of his nation at that point was sealed.
In contrast, Moses instructed his people to obey - to keep the Passover, and to sprinkle the blood of the lamb over their doorposts.
The result of his faithful obedience? Salvation.
The Destroyer did not touch them, but passed over each household covered by the blood in clemency and mercy simply because they believed enough to take the required action.
The same is true today.
Christ's death on the Cross is the once-for-all sacrifice pointed to by the Jewish Passover. It is that sprinkling of His blood that satisfied God's wrath against rebellious mankind, just as the lamb's blood in Moses' time saved the people from judgment.
By faith in that sacrifice we enter into the same protection afforded all those who kept that first Passover.
It is almost certain that some under Moses' authority refused to obey and saw the death of their firstborn, just as it is possible that some Egyptians under Pharaoh's authority complied and escaped the penalty.
But the key point is that nothing else, no other action or strategy, sufficed to effect the inevitable outcome.
It boiled down to this simple equation: believe and obey to live, or be destroyed.
Nothing has changed in the past 3500 years.