Summary: What does God expect of us?
Romans 12:1 (quickview)  I beseech you therefore, brethren, by the mercies of God, that ye present your bodies a living sacrifice, holy, acceptable unto God, which is your reasonable service. 2 And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God. 3 For I say, through the grace given unto me, to every man that is among you, not to think of himself more highly than he ought to think; but to think soberly, according as God hath dealt to every man the measure of faith.
The apostle Paul, having now finished the doctrinal part of this epistle, proceeds to the practical;
Brethren - adelphos, ad-el-fos’
A - from 1 (as a connective particle) and delphus (the womb); a brother (literally or figuratively) near or remote
That ye present. The word used here commonly denotes the action of bringing and presenting an animal or other sacrifice before an altar. It implies that the action was a free and voluntary offering.
Your bodies. The bodies of animals were offered in sacrifice. The apostle specifies their bodies particularly in reference to that fact. Paul is saying, present YOURSELVES, your entire person, to the service of God.
1Co 6:15-20 Know ye not that your bodies are the members of Christ? shall I then take the members of Christ, and make them the members of an harlot? God forbid. What? know ye not that he which is joined to an harlot is one body? for two, saith he, shall be one flesh. But he that is joined unto the Lord is one spirit. Flee fornication. Every sin that a man doeth is without the body; but he that committeth fornication sinneth against his own body. What? know ye not that your body is the temple of the Holy Ghost which is in you, which ye have of God, and ye are not your own? For ye are bought with a price: therefore glorify God in your body, and in your spirit, which are God’s.
A living sacrifice. A sacrifice-Dead to sin and living by the power of Jesus Christ.
Ro 6:4 Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.
A sacrifice is an offering made to God as an atonement for sin; or any offering made to him and his service as an expression of thanksgiving or homage. It implies, that he who offers it presents it entirely, releases all claim or right to it, and leaves it to be disposed of for the honour of God. In the case of an animal, it was slain, and the blood offered; in the case of any other offering, as the firstfruits, etc., it was set apart to the service of God; and he who offered it released all claim on it, and submitted it to God, to be disposed of at his will. This is the offering which the apostle Paul is asking the Romans to make; to devote themselves to God, as if they had no longer any claim on themselves; to be disposed of by him; to suffer and bear all that he might appoint; and to promote his honour in any way which he might command.