1 John 2:4

4 Whoever says, "I have come to know him," but does not obey his commandments, is a liar, and in such a person the truth does not exist;

1 John 2:4 In-Context

2 and he is the atoning sacrifice for our sins, and not for ours only but also for the sins of the whole world.
3 Now by this we may be sure that we know him, if we obey his commandments.
4 Whoever says, "I have come to know him," but does not obey his commandments, is a liar, and in such a person the truth does not exist;
5 but whoever obeys his word, truly in this person the love of God has reached perfection. By this we may be sure that we are in him:
6 whoever says, "I abide in him," ought to walk just as he walked.
New Revised Standard Version Bible, copyright 1989, Division of Christian Education of the National Council of the Churches of Christ in the United States of America. Used by permission. All rights reserved.