When the Pharisees heard that he had silenced the Sadducees, they came together.
Matthew 22:34

The kings of the earth take their stand, and the rulers conspire together against the LORD and his Anointed One
Psalm 2:2

And one of them, an expert in the law, asked a question to test him: “Teacher, which command in the law is the greatest?”
Matthew 22:35-36

And one of them, an expert in the law, asked a question to test him: “Teacher, which command in the law is the greatest?” He said to him, “Love the Lord your God with all your heart, with all your soul, and with all your mind. This is the greatest and most important command.
Matthew 22:35-38

“Listen, Israel: The LORD our God, the LORD is one. Love the LORD your God with all your heart, with all your soul, and with all your strength.
Deuteronomy 6:4-5

The way we love God illustrates how we understand what love is.

The fullness of humanity can be found when we love God with all of who we are
and love our neighbor as ourselves.

The second is like it: Love your neighbor as yourself. All the Law and the Prophets depend on these two commands.
Matthew 22:39-40

We love because he first loved us.
1 John 4:19