Does 1 Corinthians 3:15 promise salvation or is it a warning?

1 Corinthians 3:15
If anyone’s work is burned up, he will suffer loss, though he himself will be saved, but only as through fire.

Many proponents of free grace have used 1 Corinthians 3:15 as evidence that our salvation is guaranteed, but is this what Paul was saying? 

Hebrews 12:29 says God is a consuming fire. Isaiah was the most holy man of Israel, a man who lived in repentance and obeyed the Lord. Yet when he appeared before God's presence he was totally undone simply because he dwellt among sinners.

Isaiah 6:5
And I said: "Woe is me! For I am lost; for I am a man of unclean lips, and I dwell in the midst of a people of unclean lips; for my eyes have seen the King, the LORD of hosts!"

The presence of God is so holy that it seems to have a nature of obliterating everything that is not holy. You get a sense of this when Uzzah laid his hand on the ark of the covenant and got blasted to death because he did not go through the proper consecration rituals laid out in Leviticus (2 Samuel 6).

If God's holiness has this effect on people who are pretty righteous, what effect would it have on mouth professing Christians who say they believe in Jesus, go to church on Sundays, but live like heathens the rest of the week?

In 1 Cor 6:13 Paul says that God will destroy the stomach along with the food that is inside it. He then relates this analogy to the Corinthian believers who may be practicing sexual immorality. This is interesting because earlier in 1 Cor 3:16-17 Paul states that the believers are the temple of the Holy Spirit and warns that God will destroy them along with the practice of sin that has defiled it if they don't repent:

1 Corinthians 3:16-17 

Know ye not that ye are the temple of God, and that the Spirit of God dwelleth in you? If any man defile the temple of God, him shall God destroy; for the temple of God is holy, which temple ye are.

Now if Jesus' blood has washed our sins away, not just from a legal standpoint, but also tangibly whereby the power of sin is no longer over us and we are freed from being slaves of sin (Romans 6) whereby we can become slaves to Christ, then we have nothing to worry about because our temples will be clean and spotless. In this case, our temple would pass through God's consuming fire without a problem.

So in the preceding verse 15 Paul is talking about two things getting burned when we are judged: our works and our temples. Our salvation is not based on works, so whether or not our works are burned has no bearing on our status for inheriting eternal life. However whether or not our temples can make it through the fire *DOES* matter for salvation.

1 Corinthians 3:15 

 If any man's work shall be burned, he shall suffer loss: but he himself shall be saved; yet so as by fire. 

1 Corinthians 6:13  

Food is meant for the stomach and the stomach for food"--and God will destroy both one and the other. The body is not meant for sexual immorality, but for the Lord, and the Lord for the body. 

1 Corinthians 6:18 Flee from sexual immorality. Every other sin a person commits is outside the body, but the sexually immoral person sins against his own body. 

Matthew 10:28And do not fear those who kill the body but cannot kill the soul. Rather fear him who can destroy both soul and body in hell.

Regarding works, I believe the only works that will pass through God's fire are those that were born out of faith working through God's love.

Galatians 5:6For in Christ Jesus neither circumcision nor uncircumcision counts for anything, but only faith working through love.

A great story to read on this is Howard Pittman's testimony. He was a baptist preacher who helped raised 32 orphans, preached the gospel etc. but God showed him none of his works would pass through the fire because he did those things to soothe his own conscience and they were not born out of love.

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