While must have the proper heart regenerated by the Holy Spirit, our actions or better yet, the resulting fruit, are the tell.
Beware of false prophets, who come to you in sheep's clothing but inwardly are ravenous wolves. You will recognize them by their fruits. Are grapes gathered from thornbushes, or figs from thistles? ~ Mt 7.15-16
"What I said on Sunday wasn't nearly as important as what I did." ~ Erwin McManus, An Unstoppable Force
Directionally, I like what McManus wrote but it's still a bit short, it is ultimately about the fruit borne from right living motivated by a right heart.