If someone lied to another, and then that person spreads the lie, will the original liar get a sin for every time someone tells someone else the lie? If so, what good deeds can expiate this sin if there are a lot of lies that are spread?
One must repent from lying because it is a grave sin. If the lies entail misleading others in matters of religion or matters that result in great harm, then the liar must inform the person he lied. As for the sin, it would count as one grave sin against the liar, and all parties involved in transferring false information knowing that they are lies have also committed a sin. The only way to expiate a lie is to repent to God Almighty and seek His forgiveness after having abandoned the sin and resolving not to repeat it.