The one [A] fundamental tenet of Christianity...
You are My friends if you do what I command you. No longer do I call you servants, for a servant does not understand what his master is doing. But I have called you friends, because everything I have learned from My Father I have made known to you. You did not choose Me, but I chose you. And I appointed you to go and bear fruit—fruit that will remain—so that whatever you ask the Father in My name, He will give you. This is My command to you: Love one another.
“This is My command to you: Love one another. “
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Of course, complying with that command is one of the ways we serve Him. He did admonish us to keep the commandments.