https://www.mljtrust.org/sermons-online/john-1-45-49/the-lesson-of-nathaniel/

What is the difference between a true Christian life and someone who simply sees it as a formal religion? Is Christianity all about following the right rules and looking the right way on the outside? In this sermon on John 1:45–49, Dr. Martyn Lloyd-Jones answers these questions by diving into the life of a man named Nathaniel from the New Testament. He uses this man to show that true Christians do not view Christianity casually, but out of a sincere and concerned heart. This means a heart that is not only interested in the things of the Lord, but one that has a desire to know them. Secondly, true Christians will carefully consider what is given to them and testing it against the Scriptures. Nathaniel did just this when he was told of Jesus of Nazareth. However, Dr. Lloyd-Jones is careful to point out that although he carefully considered what was told to him (“Can anything good come out of Nazareth?”), he did not reject it all together. Those who truly desire to know the Lord must not believe everything they hear, but they also must not quench the Spirit. This is the mark of a true Christian: someone who truly desires to know Jesus Christ and who does not take the process lightly, but takes it with a concerned and sincere heart.