THOU SHALT FEAR THE ETERNAL THY G-D. The purport thereof is that after he commanded concerning the love of G-d, he mentioned that [one is] to fear Him so that he not sin and be punished.

AND HIM SHALT THOU SERVE — to do whatever He commands you, like a servant who obeys the command of his master. It is possible that this is an allusion to the Service of the offerings to His Name. And so the Rabbis have said in the Sifre¹ on the verse, After the Eternal your G-d shall ye walk, and Him shall ye fear, and His commandments shall ye keep, and unto His voice shall ye hearken, and Him shall ye serve:² "Serve Him by [studying] His Torah, serve Him in His Sanctuary.⁠" By this the Sifre meant to explain that after he admonished concerning the observance of all the commandments and hearkening to His voice, the expression and Him shall ye serve means to serve Him in the Sanctuary with offerings, songs and prostrations [that are prescribed] there. This is termed "service" as He said, I give you the priesthood as 'a service' of gift,⁠³ and it further says, And the Levites alone shall do 'the service.'⁴ The Rabbis further interpreted [in the above-mentioned Sifre]: "Serve Him through His Torah,⁠" meaning to study the Torah and meditate therein; this, too, is a "service" before Him. Accordingly, and Him shalt thou serve [mentioned in the verse before us] is also a reference to serving Him by the offerings. And Rabbi Abraham ibn Ezra wrote: "Thou shalt fear the Eternal thy G-d — you should not transgress the negative commandments; and Him shalt thou serve — fulfill the positive commandments.⁠" But this is not correct, for he stated in the other verse [mentioned above], and Him shall ye fear, and His commandments shall ye keep … and Him shall ye serve.⁠⁵

AND BY HIS NAME SHALT THOU SWEAR. This is not a commandment to swear [by His Name],⁠⁶ but it is an admonishment that [in the event one is required to take an oath] he should swear only by His Name and not by the name of another deity. After this [injunction to swear only by the name of G-d] it is written, Ye shall not go after other gods,⁠⁷ meaning that you should not follow them in any of these matters: that you not fear them, that you not serve them, and that you not swear by their names. However, in the Gemara of Tractate Temurah⁸ the Rabbis interpreted this verse to teach that a true oath is permissible.⁠⁹ Thus they said: "Why did the Merciful One state and by His Name shalt thou swear? Since it cannot refer to the oaths administered by the judges, because they have already been derived from the verse the oath of the Eternal shall be between them,⁠¹⁰ apply it to indicate that other oaths are permissible. And since it cannot refer to an oath by which one binds himself to perform a commandment, as that is derived from the expression, and to Him shalt thou cleave,⁠¹¹ then apply it to an oath about a non-sacred [i.e., a permissible, but non-obligatory] matter.⁠"
Now, I have further seen the following text in the Tanchuma:⁠¹² "The Holy One, blessed be He, said to Israel: Do not think that it has been made permissible to you to swear by My Name. You are not permitted to swear by My Name even truthfully unless you possess all these qualities: Thou shalt fear the Eternal thy G-d,⁠¹³ that you will be like those who were called 'men who fear the Eternal G-d,' such as Abraham,⁠¹⁴ Job,⁠¹⁵ and Joseph.⁠¹⁶ And Him shalt thou serve,⁠¹⁷ that you will devote yourself to [the study of] Torah and [the observance of] the commandments and you will have no other preoccupation. Therefore it is stated, and Him thou shalt serve. And to Him shalt thou cleave¹⁸ — but is it possible for a human being to cleave to the Divine Glory? Has it not been stated, For the Eternal thy G-d is a devouring fire?⁠¹⁹ But this statement is intended to teach you that whoever gives his daughter in marriage to a scholar who learns Torah and studies Mishnah, and who trades on his behalf and who benefits him from his wealth — of this He says, and to Him shalt thou cleave. If you possess all these virtues, you may swear [by My Name] and if not, you may not swear.⁠" Thus far is the text of this Agadah. Thus, the interpretation of the verse [before us], and by His Name shalt thou swear, in the opinion of the Rabbis, is a grant of permission, that He allows us, as an expression of esteem, to do so. It is as if he had said, "Thou shalt fear the Eternal thy G-d; nevertheless you may swear by His Name and you need not fear doing so.⁠" And because this permission is placed after the commands to fear G-d and to serve Him, the Rabbis inferred that there is no authorization to swear until after these virtues have been attained. Or Scripture may be stating Thou shalt fear the Eternal thy G-d and His awe will be so great upon you that His very Name will be an oath to you, so that even when you wish to confirm something you will swear by His Name even to your disadvantage and you will not misrepresent.⁠²⁰ And in the opinion of the Rabbis, the meaning of the expression and Him shalt thou serve is that you should act toward him at all times like a bondsman constantly in service before his master, considering the work of his master as primary and his own needs as casual, until, [resulting] from this [attitude] he attains what the Rabbis have said, "And let all thy deeds be done for the sake of Heaven.⁠"²¹ For even bodily needs should be for the purpose of G-d's worship. Thus a person should eat and sleep and attend to his needs to assure the existence of the body to serve G-d. This is similar to what the Rabbis have said,⁠²² "And G-d saw every thing that He had made, and, behold, it was very good²³ — this refers to sleep. Is sleep good? [It is 'good'] because, if a person sleeps a little, he rises and engages in the study of Torah.⁠"²⁴ Thus, in satisfying bodily needs, one should concentrate upon the verse I will praise the Eternal while I live; I will sing praises unto my G-d while I have my being.⁠²⁵ This is a correct interpretation.