“But the seed in the good soil, these are the ones who have heard the word in an honest and good heart, and hold it fast, and bear fruit with perseverance.” Luke 8:15 LSB https://bible.com/bible/3345/luk.8.15.LSB

How do we know we or anyone else is Christian? God describes the four ways in which people will respond to Him through His word. The first group makes no response. Immediately what they hear is taken from them, and they are not saved. The second group believes for a while but eventually falls away. They lack faithfulness to God which looks like a lack of commitment to knowing Him, working with His people, or doing His will. The third group stays much longer than the second group but loves the world more than God by worrying about and pursuing the things of the world, so they ignore the person and work of God. They lack fruitfulness. Jesus later declares the branch that bears no fruit will be cut off and burned. Not sure this group that doesn’t work toward seeing others come to faith in Jesus will enter heaven either. The only group that knows they are saved is the group that hears God’s word, keeps it, and produces fruit by sharing it. If our lives are characterized by increasing our knowledge of God through His Word, obedience to His word, and seeing people we know coming to faith because we share His word, we can be confident we are saved. These are not things we do to be saved but things that result from our salvation. The fruit of God in our lives is love for Him exhibited by our lives through obedience to everything He commanded us, the purpose of which is the seeking and saving of the lost.