I understand that the OT feasts are to a great extent fulfilled. But does Scripture say to change the manner of celebrating the Passover? Or is it an assumption on the part of some man?
The same argument can be made for Easter. The passion changes everything.
Who changed the L-rd's Passover to Easter, the Pagan feast of Ishtar of Babylon
ON THE KEEPING OF EASTER.
From the Letter of the Emperor to all those not present at the Council.
(Found in Eusebius, Vita Const., Lib. iii., 18-20.)
It was declared to be particularly unworthy for this, the holiest of all festivals, to follow the custom[the calculation] of the Jews, who had soiled their hands with the most fearful of crimes, and whose minds were blinded. In rejecting their custom,(1) we may transmit to our descendants the legitimate mode of celebrating Easter, which we have observed from the time of the Saviour's Passion to the present day[according to the day of the week]. We ought not, therefore, to have anything in common with the Jews, for the Saviour has shown us another way; our worship follows a more legitimate and more convenient course(the order of the days of the week); and consequently, in unanimously adopting this mode, we desire, dearest brethren, to separate ourselves from the detestable company of the Jews, for it is truly shameful for us to hear them boast that without their direction we could not keep this feast. How can they be in the right, they who, after the death of the Saviour, have no longer been led by reason but by wild violence, as their delusion may urge them? They do not possess the truth in this Easter question; for, in their blindness and repugnance to all improvements, they frequently celebrate two passovers in the same year. We could not imitate those who are openly in error. How, then, could we follow these Jews, who are most certainly blinded by error? for to celebrate the passover twice in one year is totally inadmissible. But even if this were not so, it would still be your duty not to tarnish your soul by communications with such wicked people[the Jews].
http://www.catholicfirst.com/thefaith/churchfathers/volume37/ecouncil3705.cfm
a bondslave to the Christ
chuck