“There are three rules in the Sacred Writings, on account of which it is not lawful for any human authority to change the time of keeping Easter, which has been prescribed to us; two whereof are divinely established in the law of Moses; the third is added in the Gospel by means of the passion and resurrection of our Lord. For the law enjoined, that the Passover should be kept in the first month of the year, and the third week of that month, that is, from the fifteenth day to the one-and-twentieth. It is added, by apostolic institution, in the Gospel, that we are to wait for our Lord’s day in that third week, and to keep the beginning of the Paschal time on the same. Which threefold rule whosoever shall rightly observe, will never err in fixing the Paschal feast. But if you desire to be more plainly and fully informed in all these particulars, it is written in Exodus, where the people of Israel, being about to be delivered out of Egypt, are commanded to keep the first Passover, that the Lord said to Moses and Aaron, ‘This month shall be unto you the beginning of months; it shall be the first month of the year to you. Speak ye unto all the congregation of Israel, saying, In the tenth day of this month, they shall take to them every man a lamb, according to the house of their fathers, a lamb for an house.’ And a little lower, ‘And he shall keep it until the fourteenth day of the same month; and the whole assembly of the congregation of Israel shall kill it in the evening.’ By which words it most plainly appears, that thus in the Paschal observance mention is made of the fourteenth day, not that the Passover is commanded to be kept on that day: but the lamb is commanded to be killed on the evening of the fourteenth day; that is, on the fifteenth day of the moon, which is the beginning of the third week, when the moon appears in the sky. And because it was on the night of the fifteenth moon, when, by the slaughter of the Egyptians, Israel was redeemed from a long captivity, therefore it is said, ‘Seven days shall ye eat unleavened bread.’ By which words all the third week of the same month is decreed to be kept solemn. But lest we should think that those same seven days were to be reckoned from the fourteenth to the twentieth, God immediately adds, ‘Even the first day ye shall put away leaven out of your houses; for whosoever eateth leavened bread, from the first day until the seventh day, that soul shall be cut off from Israel;’ and so on, till he says, ‘For in this self-same day I will bring your army out of the land of Egypt.’
“Thus he calls that the first day of unleavened bread, in which he was to bring their army out of Egypt. But it is evident, that they were not brought out of Egypt on the fourteenth day, in the evening whereof the lamb was killed, and which is properly called the Passover or Phase, but on the fifteenth day, as is most plainly written in the book of Numbers. ‘Departing therefore from Ramesse on the fifteenth day of the first month, the next day the Israelites kept the Passover with an high hand.’ Thus the seven days of unleavened bread, on the first whereof the people of God were brought out of Egypt, are to be reckoned from the beginning of the third week, as has been said, that is, from the fourteenth day of the first month, till the one-and-twentieth of the same month, that day included. But the fourteenth day is noted down separately from this number, by the name of the Passover, as is plainly made out by what follows in Exodus: where when it is said, ‘For in this same day I will bring your army out of the land of Egypt;’ it is presently added, ‘You shall keep it a feast by an ordinance for ever. In the first month, on the fourteenth day of the month at even, ye shall eat unleavened bread, until the one-and-twentieth day of the month at even. Seven days shall there be no leaven found in your houses.’ Now, who is there that does not perceive, that there are not only seven days, but rather eight, from the fourteenth to the one-and-twentieth, if the fourteenth be also reckoned in the number? But if, as by diligent study of Scripture appears to be the truth, we reckon from the evening of the fourteenth day to the evening of the one-and-twentieth, we shall certainly find, that the same fourteenth day gives its evening for the beginning of the Paschal feast; so that the sacred solemnity contains no more than only seven nights and as many days. By which our definition is proved to be true, wherein we said, that the Paschal time is to be celebrated in the first month of the year, and the third week of the same. For it is really the third week, because it begins on the evening of the fourteenth day, and ends on the evening of the one-and-twentieth.
“But since Christ our Paschal Lamb is slain, and has made the Lord’s day, which among the ancients was called the first after the Sabbath, a solemn day to us for the joy of his resurrection, the apostolic tradition has so inserted it into the Paschal festivals as to decree, that nothing in the least be anticipated, or detracted from the time of the legal Passover; but rather ordains, that the same first month should be waited for, pursuant to the precept of the Law, and accordingly the fourteenth day of the same, and the evening thereof. And when this day should happen to fall on the Sabbath, every one in his family should take a lamb, and kill it in the evening, that is, that all the churches throughout the world, composing one catholic church, should provide bread and wine for the mystery of the flesh and blood of the unspotted Lamb ‘that took away the sins of the world;’ and after the solemnity of reading the lessons and prayers of the Paschal ceremonies, they should offer up these things to the Lord, in hopes of future redemption. For that same night in which the people of Israel were delivered out of Egypt by the blood of the Lamb, is the very same in which all the people of God were, by Christ’s resurrection, delivered from eternal death. Then, on the morning of the Lord’s day, they should celebrate the first day of the Paschal festival; for that is the day on which our Lord, with much joy of pious revelation, made known the glory of his resurrection. The same is the first day of unleavened bread, concerning which it is distinctly written in Leviticus, ‘In the fourteenth day of the first month, at even, is the Lord’s Passover. And on the fifteenth day of the same month, is the feast of unleavened bread unto the Lord; seven days ye must eat unleavened bread; the first day shall be most solemn and holy.’
“If therefore it could be that the Lord’s day should always happen on the fifteenth day of the first month, that is, on the fifteenth moon, we might always celebrate Easter at the very same time with the ancient people of God, though the nature of the mystery be different, as we do it with one and the same faith. But in regard that the day of the week does not keep pace exactly with