‘You are not far from the kingdom of God’
One of the scribes came up to Jesus and put a question to him, ‘Which is the first of all the commandments?’ Jesus replied, ‘This is the first: Listen, Israel, the Lord our God is the one Lord, and you must love the Lord your God with all your heart, with all your soul, with all your mind and with all your strength. The second is this: You must love your neighbour as yourself. There is no commandment greater than these.’ The scribe said to him, ‘Well spoken, Master; what you have said is true: that he is one and there is no other. To love him with all your heart, with all your understanding and strength, and to love your neighbour as yourself, this is far more important than any holocaust or sacrifice.’ Jesus, seeing how wisely he had spoken, said, ‘You are not far from the kingdom of God.’ And after that no one dared to question him any more.
You shall love the Lord your God with all your heart
Moses said to the people: ‘If you fear the Lord your God all the days of your life and if you keep all his laws and commandments which I lay on you, you will have a long life, you and your son and your grandson. Listen then, Israel, keep and observe what will make you prosper and give you great increase, as the Lord the God of your fathers has promised you, giving you a land where milk and honey flow.
‘Listen, Israel: the Lord our God is the one Lord. You shall love the Lord your God with all your heart, with all your soul, with all your strength. Let these words I urge on you today be written on your heart.’
Source: Jerusalem Bible
Catechism of the Catholic Church
“I Believe In One God”
200 These are the words with which the Niceno-Constantinopolitan Creed begins. The confession of God’s oneness, which has its roots in the divine revelation of the Old Covenant, is inseparable from the profession of God’s existence and is equally fundamental. God is unique; there is only one God: “The Christian faith confesses that God is one in nature, substance and essence.”
201 To Israel, his chosen, God revealed himself as the only One: “Hear, O Israel: The LORD our God is one LORD; and you shall love the LORD your God with all your heart, and with all your soul, and with all your might.” Through the prophets, God calls Israel and all nations to turn to him, the one and only God: “Turn to me and be saved, all the ends of the earth! For I am God, and there is no other.. . To me every knee shall bow, every tongue shall swear. ‘Only in the LORD, it shall be said of me, are righteousness and strength.'”
202 Jesus himself affirms that God is “the one Lord” whom you must love “with all your heart, and with all your soul, and with all your mind, and with all your strength”.6 At the same time Jesus gives us to understand that he himself is “the Lord”. To confess that Jesus is Lord is distinctive of Christian faith. This is not contrary to belief in the One God. Nor does believing in the Holy Spirit as “Lord and giver of life” introduce any division into the One God:
We firmly believe and confess without reservation that there is only one true God, eternal infinite (immensus) and unchangeable, incomprehensible, almighty and ineffable, the Father and the Son and the Holy Spirit; three persons indeed, but one essence, substance or nature entirely simple.
A prayer of David. Hear, LORD, my plea for justice; pay heed to my cry; Listen to my prayer spoken without guile.
From you let my vindication come; your eyes see what is right.
You have tested my heart, searched it in the night. You have tried me by fire, but find no malice in me. My mouth has not transgressed
as humans often do. As your lips have instructed me, I have kept the way of the law.
My steps have kept to your paths; my feet have not faltered.
I call upon you; answer me, O God. Turn your ear to me; hear my prayer.
Show your wonderful love, you who deliver with your right arm those who seek refuge from their foes.
Keep me as the apple of your eye; hide me in the shadow of your wings
from the violence of the wicked.
My ravenous enemies press upon me; they close their hearts, they fill their mouths with proud roaring.
Their steps even now encircle me; they watch closely, keeping low to the ground,
Like lions eager for prey, like young lions lurking in ambush.
Rise, O LORD, confront and cast them down; rescue me so from the wicked.
Slay them with your sword; with your hand, LORD, slay them; snatch them from the world in their prime. Their bellies are being filled with your friends; their children are satisfied too, for they share what is left with their young.
I am just – let me see your face; when I awake, let me be filled with your presence.
Source: The New American Bible