The number of firstborn males after Israel left Egypt was remarkably small (around 20,000, Num. 3:43). Women in most primitive societies have an average of 7 births. this would mean that given a total population of around 2,800,000 on leaving Egypt (Ex. 12:37), there should have been around 400,000 firstborn males. But instead, there is only a fraction of this number. Why? Did Israel eat the Passover?
My suggestion- and this is well in the category of things you will never know for sure and can only ponder- is that many Hebrew firstborns died on Passover night. Israel were warned that if they did not properly keep the Passover, “the Destroyer” Angel would kill their firstborn (Ex. 12:23). “The Destroyer” is mentioned in 1 Cor. 10:10: “Neither murmur ye, as some of them also murmured, and were destroyed of the Destroyer” (olothreutes; this is a proper noun in the Greek). Who was the Destroyer? If Scripture interprets Scripture, it was the ‘Destroyer’ Angel of Passover night. In similar vein Heb. 11:28 speaks of “He (the Angel) that destroyed (Gk. olothreuo) the firstborn”.
Israel were side-tracked from what should have been the central object of their attention: the blood of the lamb. They were disobedient from the day God knew them, i.e. Passover night (Dt. 9:24). They ate the Passover, but murmured under their breath; and it was because of this murmuring, this obsession with chips on their shoulder against their leaders, the petty grumbles of life, a failure to be awed by the wonder of the redemption through that Paschal lamb...that they shared Egypt’s judgment. Did Israel properly eat the Passover? Very soon afterwards, the people reminded Moses of this incident: “Would to God we (maybe this is the emphasis) had (also) died by the hand of the Lord (a phrase often associated with Angel’s work at passover: Josh. 4;24; Is. 11:11; 19:16; Dan. 9:15; Heb. 8:9) in the land of Egypt, when we sat by the flesh pot (Young’s Literal) and when we did eat bread” (Ex. 16:3). They weren’t just saying they wished they had died in Egypt; they wished they had died by the hand of the Lord. Sitting by the flesh pot and eating bread is perhaps a reference to eating Passover that night, when in (perhaps) 90% of Hebrew families the firstborn had slumped down in death. They wished they too had died that Passover night. They felt Moses was going to kill them as, by implication, they blamed him for killing the firstborn.
Israel were intensely disobedient to God from the time of their exodus from Egypt, even before their deliverance from the Red Sea (Dt. 9:24 = Ex. 20:5,6). Perhaps this was because Moses’ faithful keeping of the Passover meant that the Angel which destroyed the (Egyptian and Hebrew) firstborn did not destroy the whole of Israel as God had initially planned (Heb. 11:28). Perhaps it was because of this righteousness which God imputed to Israel at that time that He makes no specific mention of their huge failure.
Israel’s exodus from Egypt on Passover night was a type of our exodus from the world at the second coming (Lk. 12:35,36 = Ex. 12:11). The firstborns represent us, the ecclesia of firstborns (Heb. 12;23 Gk.). Perhaps 90% of the firstborns failed to be delivered because they murmured, they allowed themselves to be distracted from the fundamental basis of their redemption: the blood of the lamb. What percentage will it be for the new Israel?