Caissie, First of all, thank you for the compliment.
Now for your questions. Peter was a Jew, and as such, if he was living under the law, was obligated to keep the law entirely. It, however, was not a matter of
knowing Christ died for his sins, for intellectual knowledge is not what saves (remember, even the demons know there is one God, and fear). Sometime between the night of betrayal and his writing of the letters included in the New Testament (most assume it was at Pentecost, and I am in no position to disagree!), the old Peter died and he was reborn in Christ, with a new heart. He was a CHRISTian -- a follower, a believer. As such, he was no longer judged under the law, even though the law still stood as judgment for those not believers. You see, 'believing' as used in the New Testament was a whole lot more than intellectual acknowledgment. It was acting in accordance to what was believed. It was 'walking the walk' and not just 'talking the talk.' If Peter had not been a believer, then, as a bar mitzvah'd Jew, aware of the Law, he would have been obligated to keep all of it, including the instructions regarding diet.
Your second question asked what we are to learn regarding eating from Acts 10. The Lord answered that: "Do not call anything impure the Lord has made clean." What is interesting about that is that it does not say "what the Lord has made," but, rather, "what the Lord has made clean." You see, Peter was presented with a sheet of all sorts of beasties which were unclean in Jewish law. But that sheet had come down from heaven, not up from earth, indicating that the Lord had thus made them clean. There is no indication, by the way, that this would apply to all lizards and birds and such forever after. But these particular ones were offered to Peter to eat, having been made clean.
Many times we are aware of someone who was a horrid person, but who is now truly born again in Christ, and is a new person. The Lord has made them clean. That is the first lesson -- and one which Peter understood. Cornelius was someone the Lord had made clean. Peter could interact freely with him as a brother in Christ.
Today, when we say grace before a meal, we are, in asking for the food to be blessed, asking for it to be -- in Jewish terms -- made clean! Does that mean one does not have to say grace before a kosher meal? That's something for others to pick apart -- I prefer to thank God for all my sustenance and ask Him to bless it to His use through my body!
I hope that answers your questions. Or at least responds decently to them!
Grasshopper, I really disagree with you, I'm afraid. Genesis 1:1 states that
In the beginning, God created the heavens and the earth. Genesis 1 then goes on to describe the formation/creation of the physical universe, the earth, and life on the earth. There is NOTHING to indicate that this meaning has changed when Jesus speaks of heaven and earth in Matthew 5. In addition, not everything is yet accomplished, for we are all here in this creation, and there is to be an end to this creation when the elements will be destroyed and a new creation made.
Your examples of Jesus' words about murder and adultery are not changes of the law at all. The outward expressions are to be judged by man. But God judges the heart, and the root of all sin lies in the heart of man. Look at the Ten Commandments. The first is a heart matter, while the second is how that heart matter of worship is to be acted upon (or not to be acted upon). The third commandment has to do with attributing actions and speech to the Lord which are not from Him! The fourth is both a heart and a lifestyle matter. Commandments five through nine have to do with physical actions and words. Thus, Jesus defined a couple of them in terms of the heart, exposing their roots. The tenth commandment closes off with reference to the heart again, and coveting. Whether or not one does anything about it, in other words, coveting is wrong. Jesus actually expanded on the meaning of this quite thoroughly in Matthew 6:25-34. He defined it in the root terms of worry.
If you think about it, most people do most things because of fear: fear of poverty or lack of respect or unknown harms or whatever. So we hedge ourselves in with various insurances, monetarily, educationally, etc. Coveting has one foot in worry and the other in selfishness. Jesus dealt with both of these 'feet' in the Sermon on the Mount. Matthew 7:12 deals with selfishness in one sentence.
The Law never changed. Jesus simply explained it in deeper terms. What we do and say physically are simply expressions of who we are spiritually. This was a major lesson Jesus dealt with a number of times.
