throw the first stone?

It means no one is without sin, so no one should throw stones.

I take it you are asking about the passage from the bible where an adulterous woman was brought to Jesus by the Pharisees and he was asked to judge her.

Instead Jesus knelt and began writing something - some bible scholars' opinions differ, but it was most likely Jesus was writing down their sins, or maybe a quote from the Holy Book. When the Pharisees insisted on Jesus judging the woman, he said those words to them, and they left, albeit begrudgingly.

The woman, surprised by this turn of events, asked Jesus why she was not stoned to death (the standard punishment for adultery of the day) and he simply dismissed her with a reminder: do not repeat that sin.

In Biblical times people were stoned to death (rocks not drugs) for various sins. Jesus saw a prostitute about to be stoned in the streets and told her accusers "let he who is without sin cast the first stone" in other words why are you judging this woman when you yourselves have not dealt with the sin in your own lives. Everyone put the rocks down and the woman left prostitution.

It can be explained in this way: people who have completely pure heart, without any envy, they have right to point out our faults, and in doing so they help us to overcome our faults. Or, if I am senior I can also point out some fault of a junior person in the mood of serving them, not with some lording it over mentality or thinking to put them down. However, usually people say something bad about others because of envy, because of desire to establish that they are better, because they want to see the faults of others, not their own faults. So we should avoid criticizing others, unless we can do something to help them and unless we are actually in the position of being able to help them. We should first focus on our own faults and try to overcome them.

Lar,

Some idiots here think that it means that you can't debate anything, as in argue.

That verse needs to be applied to the context of the story. They were going to stone a whore. Jesus was told that the Law said they had to stone her. He was asked what He thought they should do, and He said the paraphrase you did above.

It doesn't mean you can't disagree or argue.

People piss me off sometimes.

It means since we are ALL sinners no one should be pointing fingers at anyone else. So the "perfect" family man who cheats on his taxes has no right to cast aspersions on the crack addicted thieving rapist.

It means the same as, before you remove the thorn out of my eye, take the log out of yours.

It means we shouldn't judge each other, since we're all sinful.

It means that no one is perfect so don't criticize anyone else because you are not perfect yourself.

Great, but what's your point?