Lutheran: How can evangelicals read that verse, spoken by our Lord himself, and somehow still believe that baptism is simply OUR public profession of faith?
Some ancient manuscripts of Mark’s Gospel contain these verses and others do not, which presents a puzzle for scholars who specialize in the history of such manuscripts. This longer ending is missing from various old and reliable Greek manuscripts (esp. Sinaiticus and Vaticanus), as well as numerous early Latin, Syriac, Armenian, and Georgian manuscripts. Early church fathers (e.g., Origen and Clement of Alexandria) did not appear to know of these verses. Eusebius and Jerome state that this section is missing in most manuscripts available at their time. And some manuscripts that contain vv. 9–20 indicate that older manuscripts lack the section. On the other hand, some early and many later manuscripts (such as the manuscripts known as A, C, and D) contain vv. 9–20, and many church fathers (such as Irenaeus) evidently knew of these verses. As for the verses themselves, they contain various Greek words and expressions uncommon to Mark, and there are stylistic differences as well. Many think this shows vv. 9–20 to be a later addition. In summary, vv. 9–20 should be read with caution. As in many translations, the editors of the esv have placed the section within brackets, showing their doubts as to whether it was originally part of what Mark wrote, but also recognizing its long history of acceptance by many in the church.
now to answer the specific question, assuming mark 16:16 is original,i quote again (for the sake of time, i am quoting people/positions that articulate succinctly my own position)
Mark 16:16 does not say that baptism is a requirement for salvation. Let me show you why. I could easily say that he who believes and goes to church will be saved. That is true. But it is belief that saves, not belief and going to church. Likewise, if you believe and read your Bible, you'll be saved. But it isn't reading your Bible that saves you. Rather, belief in Christ, in His sacrifice, is what saves. As I've stated in other papers on this subject, there are numerous verses that clearly demonstrate that justification is by faith (Rom. 5:1; Eph. 2:8; Phil. 3:9; etc.). Belief in what God has done on the cross as a sacrifice, not what man can do by believing and getting baptized, is what results in salvation. Baptism is simply a public demonstration of the inner work of regeneration. This is why the rest of the verse says, "...but he who does not believe will be condemned," Mark 16:16 focuses on the issue of belief, not baptism. Notice that it does not say that he who is not baptized will not be saved. It never says that anywhere in scripture. - matt slick
this next one is lengthy,but thorough...
it is quite clear from such passages as Acts 15 and Romans 4 that no external act is necessary for salvation. Salvation is by divine grace through faith alone (Romans 3:22, 24, 25, 26, 28, 30; 4:5; Galatians 2:16; Ephesians 2:8-9; Philippians 3:9, etc.)
It is possible that to a first-century Jewish audience (as well as to Peter), the idea of baptism might incorporate both the spiritual reality and the physical symbol. In other words, when one spoke of baptism, he usually meant both ideas--the reality and the ritual. Peter is shown to make the strong connection between these two in chapters 10 and 11. In 11:15-16 he recounts the conversion of Cornelius and friends, pointing out that at the point of their conversion they were baptized by the Holy Spirit. After he had seen this, he declared, "Surely no one can refuse the water for these to be baptized who have received the Holy Spirit..." (10:47).The point seems to be that if they have had the internal testimony of the Holy Spirit via spiritual baptism, there ought to be a public testimony/acknowledgment via water baptism as well. This may not only explain Acts 2:38 (viz., that Peter spoke of both reality and picture, though only the reality removes sins), but also why the NT speaks of only baptized believers (as far as we can tell): Water baptism is not a cause of salvation, but a picture; and as such it serves both as a public acknowledgment (by those present) and a public confession (by the convert) that one has been Spirit-baptized.