The Bronze Serpent

Then they set out from Mount Hor by the way of the Red Sea, to go around the land of Edom; and the people became impatient because of the journey.
The people spoke against God and Moses, "Why have you brought us up out of Egypt to die in the wilderness? For there is no food and no water, and we loathe this miserable food."
The LORD sent fiery serpents among the people and they bit the people, so that many people of Israel died.
So the people came to Moses and said, "We have sinned, because we have spoken against the LORD and you; intercede with the LORD, that He may remove the serpents from us." And Moses interceded for the people.
Then the LORD said to Moses, "Make a fiery serpent, and set it on a standard; and it shall come about, that everyone who is bitten, when he looks at it, he will live."
And Moses made a bronze serpent and set it on the standard; and it came about, that if a serpent bit any man, when he looked to the bronze serpent, he lived. (Numbers 21:4-9 NASB)

Fiery serpents bit the people and many people died, but anyone who were bitten looked to the bronze serpent shall live. First, the people were bitten by the fiery serpent and they realized that they will die. They requested for a solution and were told to look at the bronze serpent. Those who believed, looked, and were saved.

"As Moses lifted up the serpent in the wilderness, even so must the Son of Man be lifted up; so that whoever believes will in Him have eternal life. (John 3:14-15 NASB)

When fiery serpents bite you, you know. But you may not know that you are a sinner. Those bitten by the serpent looked at the bronze serpent and they can see that they are healed from the bite. But when you know you are a sinner, you believe in Jesus, how do you know that you are saved?

So the difference between being saved from snake bites and saved from sin is that snake bites are physical and obvious. When you are bitten by a snake, you are bitten by a snake. When the snake bite healed, it is healed.

Sins are spiritual and you continue to sin in your flesh after salvation. While your belief changed your standing with God, it may not be so obvious to you that you are already saved.