The number 15

Rest, deliverance, stepping stone to freedom

Fifteen follows directly from fourteen in Israel's calendar: the Passover lamb was killed on the fourteenth (Exodus 12:6), and Israel began the Feast of Unleavened Bread, the walk out of Egypt itself, on the fifteenth (Leviticus 23:6). The same day of the month later marks the second day of deliverance from Haman at Purim (Esther 9:18, 21), and God added Hezekiah fifteen years of life after his illness (2 Kings 20:6). Paul's ship also sounded fifteen fathoms the same night Luke counts as the fourteenth of the storm (Acts 27:27-28). E. W. Bullinger's Number in Scripture (ch. "Fifteen") reads it as 3x5, divine perfection acting through grace, calling it a number tied to acts "wrought by the energy of Divine grace." The rest-and-freedom sense fits Leviticus 23 well; hold the arithmetic itself as Bullinger's proposal, not a rule Scripture states.

The mathematics

15 = 3 × 5, and the fifth triangular number (1 + 2 + 3 + 4 + 5).
It is the magic constant of the three-by-three square: arrange one through nine correctly and every row, every column and both diagonals come to fifteen.
15 = 2⁴ − 1, written 1111 in binary — four ones and nothing else.
The fourth Bell number: there are exactly fifteen ways to sort four things into groups.

Every property here was checked before it was printed.

What they have said about this number

Acts wrought by the energy of divine grace — three times five. Bullinger notes too that the Hebrew letters for fifteen, yod and he, spell Jah.

“Five is, as we have seen, the number of grace, and three is the number of divine perfection. Fifteen, therefore, specially refers to acts wrought by the energy of Divine grace.”

E. W. Bullinger, Number in Scripture (1894)

“Rest, and overcoming death.”

Troy Brewer, Numbers That Preach (2007)

In Hebrew and Greek

Hebrew

Chamishah asar (חֲמִשָּׁה עָשָׂר) - fifteen

Greek

Dekapente (δεκαπέντε) - fifteen

First occurrence

Genesis 5:10

And Enos lived after he begat Cainan eight hundred and fifteen years, and begat sons and daughters:

The pattern in Scripture

Feast of Unleavened Bread on 15th
Feast of Tabernacles on 15th (Lev 23:34)
Hezekiah given 15 more years (2 Kings 20:6)

Key verses

Genesis 5:10

And Enos lived after he begat Cainan eight hundred and fifteen years, and begat sons and daughters:

Genesis 7:20

Fifteen cubits upward did the waters prevail; and the mountains were covered.

Genesis 25:7

And these are the days of the years of Abraham’s life which he lived, an hundred threescore and fift...

Exodus 16:1

And they took their journey from Elim, and all the congregation of the children of Israel came unto ...

Exodus 27:14

The hangings of one side of the gate shall be fifteen cubits: their pillars three, and their sockets...

15:15 verses

Genesis 15:15

And thou shalt go to thy fathers in peace; thou shalt be buried in a good old age.

Exodus 15:15

Then the dukes of Edom shall be amazed; the mighty men of Moab, trembling shall take hold upon them;...

Leviticus 15:15

And the priest shall offer them, the one for a sin offering, and the other for a burnt offering; and...

Numbers 15:15

One ordinance shall be both for you of the congregation, and also for the stranger that sojourneth w...

Deuteronomy 15:15

And thou shalt remember that thou wast a bondman in the land of Egypt, and the Lord thy God redeemed...