The first Commandment is: “I am the Lord your God. You shall have no gods except me.” (Exodus 20:2-3). The five books of Moses (the Pentateuch) are the most important books in the Old Testament, and the giving of the Ten Commandments is the important highlight of the Pentateuch. Monotheism (belief in the one supreme God) is one of the main themes of the Pentateuch, and the first Commandment is the foundation of the Ten Commandments.

A simple way to learn each of the Commandments is to remember the list of good things that a particular Commandment requires us to do and the list bad things that the Commandment forbids us to do.

In the first Commandment, we are commended to believe, hope, love, and worship, and are forbidden to commit sins against faith, hope, charity, and worship.

Faith

According to the Baltimore Catechism, faith obliges us to do three things. First, to make efforts to find out what God has revealed; second, to believe firmly what God has revealed; and third, to profess our faith openly whenever necessary.

We sin against faith by neglecting the study of it, by doubting the doctrines of faith, and by denying the faith.

We should study the faith by reading good Catholic materials, and we must safeguard our faith by avoiding materials against the Catholic faith.

Regarding the duty to believe firmly, Bishop LaRavoire Morrow wrote, “Once we are sure God has revealed something, we must believe it. Faith does not require us to believe anything contrary to reason. Even if we cannot understand what is revealed, like the mystery of the Blessed Trinity, we act according to reason in believing it, for our reason tells us God cannot err, lie, or deceive nor be deceived.”

A person denies his faith in action by leaving the Catholic Church and join another religion, or by identifying himself with other religions.

Hope

The objects of supernatural hope are eternal life and the means to eternal life. Hence, we hope for glory and grace.

The sins against hope are presumption and despair. To be saved, we need both the grace of God, and our cooperation with it by good works. A person sins by presumption when he trusts that he can be saved by his own efforts without God’s help, or by God’s help without his own efforts.

Despair is the giving up of hope. A person sins by despair when he deliberately refuses to trust that God will give him the necessary grace to save his soul.

God the Father told St. Catherine of Siena, “Despair is that sin which is pardoned neither here nor hereafter, and it is because despair displeases me so much that I wish them to hope in my mercy at the point of death, even if their life have been disordered and wicked.”

Charity

Charity obliges us to love God above all things and to love others as ourselves for the love of God.

Any mortal sin is against charity, for by mortal sin a person puts love for creature above love for God.

According to the Baltimore Catechism, the chief sins against charity are hatred of God and of our neighbor, envy, sloth, and scandal.

Worship

We should strive to pray much and to pray well. We sin against the first Commandment by neglecting prayer and by deliberately not praying well.

The first Commandment also forbids superstition (attributing to a creature power that belongs to God alone), sacrilege (mistreats sacred person, places, or things), and simony (buying or selling spiritual things).

“We love God, because we know Him; we adore Him, because we cannot comprehend Him”, St. Gregory of Nazianzen said.

第一誡：「我是上主你的天主。除我以外，你不可有別的神。」 (出谷紀 20:2-3) 。梅瑟五書是舊約中最重要的部份；而五書中的精要就是天主十誡。「只有一個天主」是梅瑟五書的中心思想；而第一誡就是十誡的基礎。

簡單的方法去認識每一個誡命，是要回想誡命中要求我們去做的好事；和禁止我們做的一系列的壞事。

第一誡中，命令我們要實踐信、望、愛和欽崇，也禁止我們去作違背信、望、愛和欽崇的事。

信德

根據教理問答，信要求我們做三件事。第一，努力尋找天主給我們啟示的一切。第二，深信天主啟示的一切。第三，當需要的時候，要公開承認我們的信仰。

我們忽略去研究信仰，懷疑信仰的教義，否認信仰都是違反信仰的罪過。

我們要閱讀好的宗教書籍，和避免違反信仰的書籍，以保護我們的信仰。

有關深信的責任，類斯.莫隆主教主教曾經寫過：「一旦我們肯定了天父所啟示的道理，我們便要相信它。信仰並沒有要我們相信違反理智的事物。縱然我們不能理解所啟示的道理 (例如聖三的道理)，我們相信這些道理也是乎合理智的，因為理智告訴我們天主不能差錯，祂不會說謊，不欺騙人，也不會受騙。」

一個人離開天主教，參加其他的宗教，便是否認他的信仰。

望德

超性望德的對象是永恆的生命(天堂)和達至永恆生命的幫助(聖寵)。

違返望德的罪過在於妄望和絕望。要能夠得救，我們要靠天主的恩寵，但也要配合天主的恩寵而努力行善。若有人不肯努力去守誡命，又認為天主自會救他的靈魂，便是妄望；若有人認為只憑己力而不需要天主的恩寵和聖事便能夠得救，這也是妄望。

絕望是放棄希望。人故意去拒絕相信天主會給他需要的恩寵去拯救他的靈魂。

天父告訴聖女加大利納：「絕望是現今或將來都不得寬恕的，因為絕望是那樣的不悅於我，我願意他們在死時盼望我的慈悲，不管他們的生命曾是多蹇多潦倒。」

愛德

愛德要求我們愛天主在萬有之上，又要求我們為了愛天主而去愛人如己。

所有的大罪都是與愛德相反的，因為大罪把對受造物的愛放在對天主的愛之上。

根據要理問答，違返愛德的主要罪過是憎恨天主和近人、怠惰、嫉妒和立壞表樣。

欽崇

我們要努力去勤行祈禱和善作祈禱。要是我們忽略祈禱或故意在祈禱中分心走意，我們便在第一誡上犯錯了。

第一誡也禁止迷信、褻聖、和買賣聖職。

聖額我略納齊盎說：「我們愛天主，因為我們認識他；我們欽崇祂，因為我們不能完全理解祂。」