Philo on Passover

The Special Laws 2,147-149:
XXVII. (145) And after the feast of the new moon comes the fourth festival, that of the passover, which the Hebrews call pascha, on which the whole people offer sacrifice, beginning at noonday and continuing till evening. (146) And this festival is instituted in remembrance of, and as giving thanks for, their great migration which they made from Egypt, with many myriads of people, in accordance with the commands of God given to them; leaving then, as it seems, a country full of all inhumanity and practising every kind of inhospitality, and (what was worst of all) giving the honour due to God to brute beasts; and, therefore, they sacrificed at that time themselves out of their exceeding joy, without waiting for priests. And what was then done the law enjoined to be repeated once every year, as a memorial of the gratitude due for their deliverance.
These things are thus related in accordance with the ancient historic accounts. (147) But those who are in the habit of turning plain stories into allegory, argue that the passover figuratively represents the purification of the soul; for they say that the lover of wisdom is never practising anything else except a passing over from the body and the passions. (148) And each house is at that time invested with the character and dignity of a temple, the victim being sacrificed so as to make a suitable feast for the man who has provided it and of those who are collected to share in the feast, being all duly purified with holy ablutions.
And those who are to share in the feast come together not as they do to other entertainments, to gratify their bellies with wine and meat, but to fulfil their hereditary custom with prayer and songs of praise. (149) And this universal sacrifice of the whole people is celebrated on the fourteenth day of the month, which consists of two periods of seven, in order that nothing which is accounted worthy of honour may be separated from the number seven. But this number is the beginning of brilliancy and dignity to everything. Philo deals with the Passover in several texts. You may find further texts here: http://www.earlychristianwritings.com/yonge/.
The translation here is taken from the old translation of Philo, o. A., & Yonge, C. D. (1996, c1993). The works of Philo : Complete and unabridged. Peabody: Hendrickson.