“If you keep My commandments, you will abide in My love; just as I have kept My Father’s commandments and abide in His love.” (John 15:10)

Why did He tell all this to us?
So that our “joy” may be “full”.

“These things I have spoken to you so that My joy may be in you, and that your joy may be made full.” (John 15:11)

What Christ means by obey “His Commands” and by that we remain in “God’s Love”? (John 15:10)

What are “His Commands”? (John 15:10)
Is it “paying tithes” or “keeping the Sabbath”?
Which Commands is He referring to?

Answer: “His Command” is “Love one another” as He mentions after the verse above:

“This is My commandment, that you love one another, just as I have loved you.” (John 15:12)

The “plural – Commands” are both “Love”; namely, “Love God” & then “Love others”. Here are the verses to prove this which sums up the “Law & Prophets”:

“Jesus replied: “ ‘Love the Lord your God with all your heart and with all your soul and with all your mind.’

This is the first and greatest commandment.

And the second is like it: ‘Love your neighbor as yourself.’ All the Law and the Prophets hang on these two commandments.” (Matthew 22:37 – 40)

That is, His Command is “to Love”.

P/S:

How will you will you know if you have attained “His Command” which is “to Love” hence fulfilling the “Law and Prophets”?
By the way you “treat others” as this verse correlates ‘perfectly’ to all the above:

“In everything, therefore, treat people the same way you want them to treat you, for this is the Law and the Prophets.” (Matthew 7:12)