"The most important is, 'Hear, O Israel: Yahweh our God, YHWH is one. And you shall love YHWH your God with all your heart and with all your soul and with all your mind and with all your strength.' The second is this: 'You shall love your neighbor as yourself.' There is no other commandment greater than these." ~ Mark 12:29-31
If the Bible is true (and we believe it is), then the most loving and eternally significant thing you can do for someone is to share the Gospel with them. Jesus said, make disciples, not church members. The Kingdom of God is not confined within the walls of organized religion. No Church organization has a monopoly on the Truth or a franchise on God. The Church Jesus built is a Body of Believers following HIM, not following a denomination or celebrity pastor.
"Go, therefore, and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe everything I have commanded you. And remember, I am with you always, to the end of the age." ~ Matthew 28:19-20