Why do SO many things take “40 days and 40 nights” in the Bible?
Do you think there’s a deeper reason why the Bible uses this time frame?
Is it symbolic, literal, or both?
40 is typically seen as a number that indicates a time of preparation.
In the cases provided in the OP, I suspect that these are examples of what could be called “biblical hyperlinking”. A hyperlink, in the context of a website on the internet, links together pages. Or one can imagine how hyperlinks work on Wikipedia where ideas and concepts are shared and referenced.
Biblical authors frequently “hyperlink” ideas from earlier texts, to bring those older concepts into their work. When Jesus fasted for forty days and forty nights in the wilderness, this seems like a clear example of “hyperlinking” to Moses’ time of fasting; Jesus does this as a voluntary time of preparation and the Evangelists mention it because a major theme in the Gospels (and the New Testament more broadly) is the ways in which Jesus is a Moses figure, fulfilling the prophecy that God would raise up a prophet like Moses, and so there are many ways in which Jesus parallels Moses pointing to Jesus as the fulfillment of Moses–and thus the One who fulfills the Law and ushers in a New Covenant. This is probably why Matthew has Jesus giving the Sermon on a mountain (the Sermon on the Mount) where Jesus references the Law “You have heard it was said…” but then gives a fuller commandment and teaching, “But I say to you…” Because Jesus did not come to abolish the Law, but to make full the Law by fulfilling the promises of the Law, in being the singularly righteous Law-keeper (nobody else could or did), and being the One about whom the Law ultimately points.
Similar hyperlinking is probably also happening elsewhere here. The number 40 is also–looking online at a couple commentators–a “nice round number”, 40 days (and nights) is a good number of days, 40 years is a good round number to indicate about the time one generation is born and grows up to have their own children and sire the new generation.
Elijah taking 40 days and 40 nights is probably itself linking to Moses’ fast and the period of wandering in the Sinai desert, as Elijah is going to Mt. Horeb, that’s Mt. Sinai where God gave Moses the Torah. Elijah is returning, metaphorically and literally, to where God’s Covenant began; in a time when much of Israel has scorned the Covenant and the Law, and Elijah’s prophetic mission is to return the people back to God, to remember their fathers who wandered in the desert, to remember God’s promises He made back in Sinai, to return to the true worship of YHWH and reject the false gods they had come to embrace during the reign of Ahab.
Of course Elijah’s story then is hyperlinked forward to John the Baptist, as John fulfills the promise made by the Prophet Malachi that an Elijah figure would come to turn the hearts of the fathers to their sons and the hearts of sons to their fathers. Jesus says, point blank, John is the Elijah figure promised to come. So John came “in the spirit and power of Elijah”.
Biblical writers do this all the time. It’s one of the ways in which the Bible often becomes self-referential; and as we meditate on Scripture we see emerging from many different texts common themes. It’s as though the Bible is many different streams all flowing together into one large river–and that one river is Christ.