Institutes of the Christian Religion (1559) - John Calvin
Book 2 - God the Redeemer
Chapter 8 - Explanation of the Moral Law:
The 10 Commandments
Sections 51-55 - Principles of the law - loving neighbor
Section 51 - The sum of the law
Its purpose is to shape us to righteousness.
It would be a mistake to think the law only gets you part way.
The whole of God's will is found there: love God and neighbor - Deut 6:5; Lev 19:18 - from the conscience and with faith - 1 Tim 1:5.
Section 52 - Why does Scripture sometimes mention only the Second Table?
Jesus does this in Matt 23:23; 19:16-19 because our deeds of love (2nd table) show our obedience to God (1st table).
Obeying the first table is done in the intent of the heart (can't see it) or in ceremonies (can be hypocritically done). Obeying the second table makes visible and plain where our heart is. The prophets convicted Israel mostly according to the second table, too - Isa 1:17.
Section 53 - Faith and love
This doesn't mean the second table is more important: it proves our piety.
Love for neighbor is the fulfillment of the law - Rom 13:8; Gal 5:14; Matt 7:12.
Section 54 - Love of neighbor
Closest conformity to God's will is to be most fruitful for others.
Loving neighbor as self doesn't concede love of self as legit - 1 Cor 13:5.
Section 55 - Who is our neighbor?
We have greater responsibility to those with whom we are more closely linked.
But it also includes even the remotest person - Luke 10:36.