1 John 4:16b reads “God is love. Whoever lives in love lives in God, and God in them” (NIV). The version you choose doesn’t matter much as the clear thought here comes through in each one, if you “Live in Love, you live in God, and God lives in you.”
But John is here stating the inverse of the truth he first stated eight verses earlier (1 John 4:8), “Whoever does not love does not know God, because God is love.”
So how do we go about living in love? A few other verses provide a glimpse at the answer. For instance, “In this same way, husbands ought to love their wives as their own bodies. He who loves his wife loves himself” and “However, each one of you also must love his wife as he loves himself” (Hebrews 5:28 and 33a). The more I love my wife, the more I live in love, the more I live in God.
Then there’s “love your neighbor as yourself” first in Leviticus 19:18b as a commandment from YHWH and then from Jesus, his second commandment, “Love your neighbor as yourself” in Mark 12:31. This is not just for the neighbor I like, but also for the neighbor who has done me wrong, who I could reasonably bear ill will towards. This is not near so nice or as easy as loving my wife as myself. Still, if (big IF) I persevere and “love my neighbor as myself” – the more I do so the more I live in love, the more I live in God. Not so hard if I remember my wife, my bride of 40 years, is my closest neighbor and I begin there.
Finally (for the purposes of this entry) there is the command to “Love the LORD your God with all your heart and with all your soul and with all your strength” or “Love the Lord your God with all your heart and with all your soul and with all your mind and with all your strength” first in Deuteronomy 6:5 then in Mark 12:30. Note the addition of “all your mind” in Mark when Jesus give this as his first command.
How can we do this, “Love the LORD our God with all of our heart, and with all our soul, and with all our strength?” Deuteronomy 30:6, provides a clue, “The LORD your God will circumcise your hearts … so that you may love him with all your heart and with all your soul.”
But that was Old Testament, how do are we to do this now, circumcise our hearts? I don't know, but I think Jesus provides the answer in Matthew 18:3, when “he said: ‘Truly I tell you, unless you change and become like little children, you will never enter the kingdom of heaven.’”
As an adult, I need to somehow circumcise my heart to have a heart like that of a little child. I think that is the answer. The first disciples, hard bitten fishermen, did this when they dropped everything to follow Jesus. They, at that time, had the hearts of little children.
With the LORD circumcising my heart, I become like a child living in love, living in God, with God living in me.