“Abu Hurairah reported the Blessed Messenger ﷺ as saying: for those who call people to righteousness, there will be reward assured for them like the rewards of those who adhered to it, without their rewards being diminished in any respect. And those who call people to error, they shall have to carry (the burden) of its sin, like those who committed it, without their sins being diminished in any respect.”
(Sahih Muslim)
Islam enjoins the believers to call people to all that is good, and prohibit them from all that is evil. This duty forms the nucleus of the socio-religious life of the believers. This hadīth brings into light the rewards of those who take care to do this duty as well as the burden of those who do otherwise.
There are at least some people belonging to all faiths who feel pleasure in doing good. But it is Islam that enjoins the believers not to be content with doing good themselves only but to invite others as well to do good and virtuous. If a believer invites his fellow beings to do good and righteous, the Blessed Messenger ﷺ assures him a reward equal to the reward of those who adhere to the call. And, similarly, if a person invites his fellow beings to evil, he would have to bear the burden of its sin equal to those who commit the evil. There will be no diminishing of the reward or burden of sin of the adherents.