'And it came to pass, that after three days they found him in the temple, sitting in the midst of the doctors, hearing them and asking them questions. [Lk 2.46] Let us see what is meant by the three days, the temple, Jesus's sitting, the doctors, and his hearing and asking questions. . .

This may be given another interpretation. The three days stand for penitence, which consists in the three elements of contrition, confession and satisfaction. Moses said in Exodus: We will go three days journey into the wilderness, to sacrifice unto the Lord our God. [Ex 3.18] After these thee days, Joseph and Mary (the penitent in spirit, poor and humble) find Jesus in the temple of the heavenly Jerusalem; which is foreshadowed in Genesis, where we are told that after three days the butler was restored to his former place [cf. Gen 40.20-21].'

St. Anthony of Padua