When the Lord brought the Israelites out of Egypt, it turns out that there were non-Israelites among them! This is a wonderful preview of how it would be in the New Age (of the NT) when God would create one man/race out of the two (Jew and Gentile):
11 Therefore, remember that formerly you who are Gentiles by birth and called "uncircumcised" by those who call themselves "the circumcision" (that done in the body by the hands of men)-- 12 remember that at that time you were separate from Christ, excluded from citizenship in Israel and foreigners to the covenants of the promise, without hope and without God in the world. 13 But now in Christ Jesus you who once were far away have been brought near through the blood of Christ. 14 For he himself is our peace, who has made the two one and has destroyed the barrier, the dividing wall of hostility, 15 by abolishing in his flesh the law with its commandments and regulations. His purpose was to create in himself one new man out of the two, thus making peace, 16 and in this one body to reconcile both of them to God through the cross, by which he put to death their hostility. Ephesians 2 NIV
And when the Israelites celebrated the passover feast, in haste, to remember how they had been brought out of Egypt in a big hurry (hence naan bread being the only bread available! The first curry houses in the world?!), there would have been some foreigners eating it with them. But those who took part in the feast had to be circumcised to show that they were counted as being among God's people. This means that today, despite our eagerness to include one and all, we do need to remember that as we gather for communion, it is believers that are welcome. Those with circumcised hearts, as Paul puts it in Romans 2.
Take a moment to read Exodus 12, especially verses 43-51:
43 Then the LORD said to Moses and Aaron, "These are the regulations for the festival of Passover. No foreigners are allowed to eat the Passover lamb. 44 But any slave who has been purchased may eat it if he has been circumcised. 45 Hired servants and visiting foreigners may not eat it. 46 All who eat the lamb must eat it together in one house. You must not carry any of its meat outside, and you may not break any of its bones. 47 The whole community of Israel must celebrate this festival at the same time. 48 "If there are foreigners living among you who want to celebrate the LORD's Passover, let all the males be circumcised. Then they may come and celebrate the Passover with you. They will be treated just as if they had been born among you. But an uncircumcised male may never eat of the Passover lamb. 49 This law applies to everyone, whether a native-born Israelite or a foreigner who has settled among you." 50 So the people of Israel followed all the LORD's instructions to Moses and Aaron. 51 And that very day the LORD began to lead the people of Israel out of Egypt, division by division. Exo 12 NLT