No, it’s not true. Nothing in scripture says a non-Jew can’t do Passover. Quite the opposite, everyone should be keeping Passover. In Numbers 15:13-16, YHWH says four times in a row that ALL who accept Him are to do exactly as HIS people do! Whether we’re “doing it right” or not is irrelevant. By “doing” we are obeying and from there, we can ultimately learn “how” to keep His Feasts.
When you get a chance, please read this article, which will help, in part, to answer your question We need to remember, we are ONE in Messiah today. There is no Temple, there is no Jew or Gentile, male or female, slave or free (Ephesians 2:15; Galatians 3:28, etc.); and “Israel” as a people, is spread all over the world.
See also Revelation 7:4-10 … especially verse 9, which says: “And after these things, I looked, and lo, a great multitude which no one could number, from all kindreds and nations and tribes and tongues; who stood before the throne and before the Lamb, clothed in white robes, and palms in their hands; 10. and they cried with a loud voice, saying: Salvation to our Elohim, to him who sits on the throne, and to the Lamb.”
ALL tribes, kindreds and nations were standing before YHWH; it was not just the Jews! And get this, during the original Passover, when Moshe led God’s people out of Egypt, all those who had killed a lamb and spread its blood on their doorposts were saved from the death of the firstborn. We’re not told that any Egyptians did this, but was YHWH really angry with the Egyptian people or with the Egyptian gods and people worshiping Egyptian Gods? Exodus 12:12 tells us "For that night, I will pass through the land of Egypt and kill all the firstborn in the land of Egypt, both men and animals; and I will execute judgment against all the gods of Egypt..."
Had an Egyptian turned from the gods of Egypt, they too could have had their firstborn spared. Moreover, YHWH said as much that the people of Egypt, including Pharaoh, would be accepted if only they turned from their gods and accepted Him!
Exodus 9:15 "By now I could have stretched out my hand and struck you and your people with such severe plagues that you would have been wiped off the earth. 16 But it is for this very reason that I have kept you alive — to show you my power, and so that my name may resound throughout the whole earth."
YHWH is ready and willing to accept all who accept him1 His favor was not intended only for the Hebrews! This is YHWH. Even in Jeremiah 25:5-6, we see YHWH's message has always been to turn only to Him: "25:5 The message was always: 'Every one of you, turn back from his evil way, from the evil of your actions. Then you will live in the land Adonai gave you and your ancestors forever and ever. 6 Don't follow other gods by serving and worshipping them. "Don't provoke my anger with things your own hands have made; then I will do you no harm."
And we are told in Exodus 12:38 that a “mixed multitude” followed Moshe out of Egypt – which included those Egyptians who had obviously been convinced about the God of Abraham, Isaac and Jacob and wanted to join Him and His people. We read: Exodus 12:38 "A mixed crowd also went up with them, as well as livestock in large numbers, both flocks and herds."
Once they followed Moshe and lived under YHWH’s rule for 40 years, you can be sure they knew who He was and kept many commands! This perfectly ties in with Numbers 15:13-16, which says:
Numbers 15: 13 "'Every citizen is to do these things in this way when presenting an offering made by fire as a fragrant aroma for ADONAI. 14 If a foreigner stays with you - or whoever may be with you, through all your generations - and he wants to bring an offering made by fire as a fragrant aroma for ADONAI, he is to do the same as you. 15 For this community there will be the same law for you as for the foreigner living with you; this is a permanent regulation through all your generations; the foreigner is to be treated the same way before ADONAI as yourselves. 16 The same Torah and standard of judgment will apply to both you and the foreigner living with you.'" (CJB)
Please re-read the above in case you missed it: Any Torah-less non-Jew/Hebrew/Israelite who does not yet believe in the God of Abraham, Isaac and Jacob is an "alien"/foreigner. However, if they do wish to accept Him, then they are to do exactly as those who are already belong to Him!
So, in Exodus 12, a mixed multitude had gone out of Egypt with Moshe and were ultimately absorbed into one of the Tribes. Eventually, YHWH had to bring the entire group back toward righteousness. In Exodus 12:43, the command was that no foreigner is to eat the Passover lamb; but Exodus 12:44 provides an expanded guidance that those "in your house" - that is, those whom are bound to you (such as slaves)- must then "do as you do" - and they should be circumcised.
Verses 45 and 48 make this even clearer as (45) "neither a traveler nor a hired servant may eat it" and (48) "If a foreigner staying with you wants to observe ADONAI's Pesach, all his males must be circumcised. Then he may take part and observe it; he will be like a citizen of the land. But no uncircumcised person is to eat it."
In Joshua 5, all the people who came out of the exodus and crossed the Jordan celebrated the Passover (Joshua 5:10), this included the descendants of the mixed multitude who departed Egypt all those years ago. All the males of the "children of Israel" were circumcised (Joshua 5:2-8). This was one body, and it included Jews and Gentiles alike - ALL who accept YHWH as their God.
Well, in the meantime, Messiah Yeshua died on our behalf, removing all the divisions, and today, there is no reason why a non-Jew who has accepted YHWH as their God and Yeshua as His Messiah cannot keep the Feast of Passover! (This is NOT to say that once someone has accepted YHWH, he shouldn’t become circumcised, because circumcision IS a sign of His covenant! (Please see our article )
But, while still learning, there is nothing saying an uncircumcised man, today, cannot partake of the Passover seder or commemorate the Exodus. The sign of circumcision, we have learned from the Messiah, is only meaningful when the individual's heart is committed.
Hebrews 10:19. We have therefore, my Brothers, assurance in entering into the sanctuary by the blood of Y’shua and by a path of life 20. which he has now consecrated for us through the veil that is his flesh. (AENT)*
*And on the other side of that “veil” is the Ruach haKodesh, (Isaiah 11:1-2, Zechariah 12:10).
So, by all means, yes, we must all, Jew and Gentile, keep Passover to the best of our ability to honor the memory of the event as commanded (see Exodus 12:14, 26-27). Get rid of all your leavened products and clean out your toaster (Exodus 12:19), and if you can manage it, do all your Passover meal preparation before sunset, and eat, and celebrate. You can still be dining after sunset, making sure to include matzah and maror (bitter herbs, i.e., horse radish) as part of the remembrance (Exodus 12:6-8).
One more thing: Celebrating via a Passover seder is both fun and rewarding! The best thing to do, if you are brand new at this, is to attend a Passover seder in your area, so you can learn the basics. If you cannot do that, you can always Google “Passover seder” and get some ideas from the various websites. In the meantime, we would recommend you obtain a copy of Barney Kasdan’s “God’s Appointed TImes” which contains historical background, traditional Jewish observance, relevance to the New Testament, prophetic significance, and a practical guide for believers, including recipes, songs, and crafts.