Today’s Catechism sections begin the discussion on the first commandment. Supporting material comes from St. John Chrysostom’s “Homily 71 on Matthew”.

CHAPTER ONE

YOU SHALL LOVE THE LORD YOUR GOD WITH ALL YOUR HEART, AND WITH ALL YOUR SOUL, AND WITH ALL YOUR MIND

2083 Jesus summed up man's duties toward God in this saying: "You shall love the Lord your God with all your heart, and with all your soul, and with all your mind."1 This immediately echoes the solemn call: "Hear, O Israel: the LORD our God is one LORD."2
God has loved us first. the love of the One God is recalled in the first of the "ten words." the commandments then make explicit the response of love that man is called to give to his God.

Article 1

THE FIRST COMMANDMENT

I am the LORD your God, who brought you out of the land of Egypt, out of the house of bondage. You shall have no other gods before me. You shall not make for yourself a graven image, or any likeness of anything that is in heaven above, or that is in the earth beneath, or that is in the water under the earth; you shall not bow down to them or serve them.3
It is written: "You shall worship the Lord your God and him only shall you serve."4

I. "You Shall Worship the Lord Your God and Him Only Shall You Serve"

2084 God makes himself known by recalling his all-powerful loving, and liberating action in the history of the one he addresses: "I brought you out of the land of Egypt, out of the house of bondage." the first word contains the first commandment of the Law: "You shall fear the LORD your God; you shall serve him.... You shall not go after other gods."5 God's first call and just demand is that man accept him and worship him.

2085 The one and true God first reveals his glory to Israel.6 The revelation of the vocation and truth of man is linked to the revelation of God. Man's vocation is to make God manifest by acting in conformity with his creation "in the image and likeness of God":

There will never be another God, Trypho, and there has been no other since the world began . . . than he who made and ordered the universe. We do not think that our God is different from yours. He is the same who brought your fathers out of Egypt "by his powerful hand and his outstretched arm." We do not place our hope in some other god, for there is none, but in the same God as you do: the God of Abraham, Isaac and Jacob.7

2086 "The first commandment embraces faith, hope, and charity. When we say 'God' we confess a constant, unchangeable being, always the same, faithful and just, without any evil. It follows that we must necessarily accept his words and have complete faith in him and acknowledge his authority. He is almighty, merciful, and infinitely beneficent. Who could not place all hope in him? Who could not love him when contemplating the treasures of goodness and love he has poured out on us? Hence the formula God employs in the Scripture at the beginning and end of his commandments: 'I am the LORD.'"8

IN BRIEF

2133 "You shall love the Lord your God with all your heart, and with all your soul and with all your strength" (⇒ Deut 6:5).

2134 The first commandment summons man to believe in God, to hope in him, and to love him above all else.

St. John Chrysostom in his “Homily 71 on Matthew” discusses the first commandment.

For since the first commandment was this, You shall love the Lord your God, thinking that He would afford them some handle, as though He would amend it, for the sake of showing that Himself too was God, they propose the question. What then says Christ? Indicating from what they were led to this; from having no charity, from pining with envy, from being seized by jealousy, He says, You shall love the Lord your God. This is the first and great commandment. And the second is like this, You shall love your neighbor as yourself. Matthew 22:37-39

But wherefore like this? Because this makes the way for that, and by it is again established; For every one that does evil hates the light, neither comes to the light; John 3:20 and again, The fool has said in his heart, There is no God. And what in consequence of this? They are corrupt, and become abominable in their ways. And again, The love of money is the root of all evils; which while some coveted after they have erred from the faith; 1 Timothy 6:10 and, He that loves me, will keep my commandment.

But His commandments, and the sum of them, are, You shall love the Lord your God, and your neighbor as yourself. If therefore to love God is to love one's neighbor, For if you love me, He says, O Peter, feed my sheep, John 21:16-17 but to love one's neighbor works a keeping of the commandments, with reason does He say, On these hang all the law and the prophets. Matthew 22:40

Footnotes

1 ⇒ Mt 22:37; cf. ⇒ Lk 10:27:". . . and with all your strength."
2 ⇒ Deut 6:4.
3 ⇒ Ex 20:2-5; cf. ⇒ Deut 5:6-9.
4 ⇒ Mt 4:10.
5 ⇒ Deut 6:13-14.
6 Cf. ⇒ Ex 19:16-25; ⇒ 24:15-18.
7 St. Justin, Dial. cum Tryphone Judaeo 11, 1: PG 6, 497.
8 Roman Catechism 3, 2,4.