12 Now, what does the number Forty-six mean? Meanwhile, how Adam extends over the whole globe, you have already heard explained yesterday, by the four Greek letters of four Greek words. For if you write the four words, one under the other, that is, the names of the four quarters of the world, of east, west, north, and south, which is the whole globe—whence the Lord says that He will gather His elect from the four winds when He shall come to judgment; — if, I say, you take these four Greek words—ἀνατολὴ, which is east; δύσις, which is west; ἄρχτος, which is north; μεσημβρία, which is south; Anatole, Dysis, Arctos, Mesembria,— the first letters of the words make Adam.
How, then, do we find there, too, the number forty-six? Because Christ's flesh was of Adam. The Greeks compute numbers by letters. What we make the letter A, they in their tongue put Alpha, α, and Alpha, α, is called one. And where in numbers they write Beta, β, which is their b , it is called in numbers two. Where they write Gamma, γ, it is called in their numbers three. Where they write Delta, δ, it is called in their numbers four; and so by means of all the letters they have numbers.
The letter we call M, and they call My, μ, signifies forty; for they say My, μ, τεσσαράχοντα. Now look at the number which these letters make, and you will find in it that the temple was built in forty-six years. For the word Adam has Alpha, α, which is one: it has Delta, δ, which is four; there are five for you: it has Alpha, α, again, which is one; there are six for you: it has also My, μ, which is forty; there have you forty-six.
These things, my brethren, were said by our elders before us, and that number forty-six was found by them in letters. And because our Lord Jesus Christ took of Adam a body, not of Adam derived sin; took of him a corporeal temple, not iniquity which must be driven from the temple: and that the Jews crucified that very flesh which He derived from Adam (for Mary was of Adam, and the Lord's flesh was of Mary); and that, further, He was in three days to raise that same flesh which they were about to slay on the cross: they destroyed the temple which was forty-six years in building, and that temple He raised up in three days.
Source: Tractates on the Gospel of John (New Advent)