That is actually the first paragraph of the Catechism, in the prologue
*1 God, infinitely perfect and blessed in himself, in a plan of sheer goodness freely created man to make him share in his own blessed life. For this reason, at every time and in every place, God draws close to man. He calls man to seek him, to know him, to love him with all his strength. He calls together all men, scattered and divided by sin, into the unity of his family, the Church. To accomplish this, when the fullness of time had come, God sent his Son as Redeemer and Savior. In his Son and through him, he invites men to become, in the Holy Spirit, his adopted children and thus heirs of his blessed life. *
Off the top of my head, I would say that it is based on Dueteronomy 6:5
Therefore, you shall love the LORD, your God, with all your heart, and with all your soul, and with all your strength. (Deuteronomy 6:5)
And Jesus’ words to the scholar who tests him in Luke 10
There was a scholar of the law who stood up to test him and said, “Teacher, what must I do to inherit eternal life?” Jesus said to him, “What is written in the law? How do you read it?” He said in reply, “You shall love the Lord, your God, with all your heart, with all your being, with all your strength, and with all your mind, and your neighbor as yourself.” (Luke 10:25-27)
Seek = strength
Know = mind
Love = heart
Also see John 17 which speaks of knowing God and Jesus revealing God to us.
Now this is eternal life, that they should know you, the only true God, and the one whom you sent, Jesus Christ. (John 17:3)
"I revealed your name to those whom you gave me out of the world. They belonged to you, and you gave them to me, and they have kept your word. Now they know that everything you gave me is from you, (John 17:6-7)
For the subject of love, nothing better than the first letter of St. John. It goes on and on about “This is love” and “This is how we know love” and “This is how we know we are loved”, etc.
-Tim-
