Then there's the "gospel" where everyone must convert to Judaism to be saved (Gal. 2:4-5, 3:10, 5:1, 18, Rom. 8:2, 10:4), but how then is the New Covenant called "freedom" and a "light yoke" if it's the same as the Old Covenant? (Matt. 11:28-30, Jam. 2:12, 2Cor. 3:4-18) Jesus fulfilled the letter of the law (as ONLY He ever could - Matt. 5:17), and we fulfill the spirit of it by yielding to the power of His Spirit IN us. The law has not passed away (Matt. 5:18), but those who are IN Jesus, who fulfilled it, are no longer under it. (Rom. 8:1-2, Col. 2:8-23, Gal. 3:23-29, Phil. 3:3, Eph. 2:15) It would not be "putting God to the test" for the Jews of the early Church to insist that Gentile believers follow the letter of the law under the New Covenant if it were actually required of them - but it isn't. (Acts 15:10-11, 24-29) The spirit of the law is and has always been genuine love working its way out - bearing "good fruit." (Rom. 6:17-18, Gal. 5:14, Eph. 6:6, Lev. 19:17-18, Matt. 22:36-40, Phil. 2:12-16, John 15:8-11, 12, 13:34-45) The opposite of that is walking "in the flesh" and what works out from that is bad fruit. (Matt. 15:18-19, 12:33, Luke 6:43-45, Gal. 5:19-21) The "fruit" in Col. 1:10 is not keeping the letter of the law, but the first, most important fruit of the Spirt - love. (Gal. 5:22-23) The "knowledge of God" in Col. 1:10 likewise is not learning about the law, which puffs up (1Cor. 8:1), but in learning His longsuffering, loving, faithful ways. (1Cor. 13:13, Eph. 4:2, Col. 3:12-17, Gal. 6:2)

Some use the rationale that God doesn't change and so "it follows" that neither does what He expects of us, but that is contradictory to the fact that there IS a NEW Covenant. (Jer. 31:31-34, Luke 22:20, 1Cor. 11:25, 2Cor. 3:6, Heb. 8:8, 9:15, 12:24) God is DOING a new thing - He's not "becoming" a new thing. (Isa. 43:18-19, John 7:38, Rev. 22:17, Jer. 21:22, 1Pet. 2:4-5, Eph. 2:22, Rev. 21:10) Besides the end of food restrictions, for example, God no longer requires the men to travel to a temple in Jerusalem three times a year (Deu. 16:16, John 4:John 4:21), or for them to be ritually circumcized. (Rom. 2:25-29, Gal. 5:2-6, 6:15) 

God didn't change, but His requirements apply to those to whom they were given. If you think of Adam and Eve populating the earth, the restrictions that came later about marrying close relatives would have certainly hindered the ability to fulfill the command to be fruitful and multiply. Likewise, it would be absurd for anyone today to build an ark to escape God's wrath to come, since the next destruction will be by fire (2Pet. 3:7, 10-12) but those who are in Jesus are "in the ark" already. (Rom. 5:9) 

{Please note that the above section was longer than the others because there is a movement gaining ground where people who sincerely desire to please God are being misled into thinking that He desires Gentile believers to obey the Old Covenant. However, people who taught such things during the early Church were strongly opposed by Paul, mostly in the book of Galatians, but also see Romans and Hebrews for more information.}

There's also the other "gospel" where everyone goes to heaven no matter what they believe - no need for a Savior, but we know better, don't we? (John 3:18, 1John 2:23, Rom. 10:8-13, Acts 4:12, Rev. 22:14-15). Or how about the one where you just say you believe and then continue indulging the same evil desires you had before you were "saved"? (Gal. 5:19-21, 13, 1Cor. 6:9-10, 15:33-34, 2Cor. 12:20-13:2, Eph. 5:5, Rev. 21:8, Rom. 6, John 8:34-36) Remember, we're responsible for obeying the commands that we were given. (John 13:14-35, Rom. 13:8-14, Gal. 5:13, Acts 21:25, 1Cor. 6:9-20, Eph. 5:5-12, Rev. 21:7-8, 22:14-15) "Love" is not the same thing as "permissiveness," and "truth" is not the same thing as "hate." (Eph. 4:15-30, 1Thess. 4:1-8)

Don't fall for any of these false gospels! The way is narrow and few find it. (Luke 13:24-30) The devil has made sure that the door leading to destruction is marked "eternal life." (John 8:44, 2Cor. 11:13-15) It's a trick and it leads to everlasting regret! (Jude 1:3-25, 2Pet. 2-3, 2Tim. 3:1-4:5, 2Cor. 7:8-10) It's not that there's a long list of things to do in order to be saved. There's just ONE item on that list - BELIEVE. (Acts 16:30-31, John 1:12-13, 3:16-18, 6:40, 11:25-26, Rom. 1:16) But those who truly believe are indwelt by the Holy Spirit, and HE brings forth good fruit. (John 14-15, 1John 4:13, Gal. 5:22-23) That's why His presence is similar to the wind - we can see the effects of the wind even though we can't see the wind itself. (John 3:3-8, Gal. 5:24-25) We don't obey out of fear, but out of LOVE. (1John 4:10-17, 18, 2Cor. 5:14-15, 1Cor. 16:22) Not to be seen by others or according to rote and ritual, but to please God. (Matt. 6:1-8, Mark 7:6-9) Not by OUR power, but HIS. (Phil. 2:12-16, Titus 2:11-3:8, Rom. 8:9) Not according to the letter of the law, but according to the SPIRIT of it. (Rom. 7:4-6, 8:13-14, 13:8-14, Matt. 7:12-29, Mark 12:28-34)

We have several lists in the Bible by which we can examine ourselves to see if our fruits are those of the Holy Spirit (regenerated, born from above) or of the flesh (still dead in sin). (2Cor. 13:5, 2Pet. 1:3-15, Col. 3, Gal. 5:13-25, 1Cor. 6:9-20, Rev. 21:7-8, 22:15, Rom. 1:24-32, Jam. 3:13-18, 1:19-24, 25-27) It's not what we have DONE before being saved (or even slipping afterwards), but what we make a practice of after we're saved. (1John 1:5-10, Rom. 2:1-11, Eph. 4:17-24, Phil. 4:8-9, Col. 3:5-25, 2Pet. 1:10, 1John 2:28-29, 3:7-10) We're not instantly perfect the moment we believe, but there will be progress toward Christlikeness. (2Pet. 1:8, Rom. 12:1-2, 8:29) 

We don't go to a particular place or through a person on earth to connect with God like they did under the Old Covenant. (John 4:20-24, 1Tim. 2:5-6, Matt. 23:8-12) The Church is not a building or a system of rituals, but the Body of Christ, which is made up of true believers. (Col. 2:23, Rom. 12:5, 1Cor. 12:27, Eph. 5:23, Col. 1:24-29) Since we believers ARE the Church, we should be earnestly seeking to reflect well upon our Savior in everything we do. (2Cor. 5:17-21) It's HIS light that we're shining. (Matt. 5:14-16, 2Cor. 4:6-7, Eph. 5:13-17, 11-12, John 8:12, 3:19-21) There will be rewards for those who do this out of love, respect for and gratitude to God for the unfathomable gift of salvation He gave us through Jesus. (Gal. 5:14, Col. 2:6-7, 3:23-25, 1Cor. 3:10-17, 2John 1:8, Matt. 5:11-13, 6:1-4, 10:37-40, 41-42, Luke 6:35, 2Tim. 3:12-13, Rev. 22:10-21) Let's all show the love of God in our thoughts, words and actions in order to honor and glorify our Lord and Savior. (Heb. 6:9-12, 1Tim. 1:5, Matt. 25:21)