אחרי ה' אלוהיך תלך, "Follow the Lord your God, etc. It is difficult to understand why our paragraph about the false prophet is interrupted by this verse. This verse should have been written only after verse 6 in which the penalty of execution of the false prophet is discussed. Besides, why did Moses use such long-winded phraseology as "you shall follow God, fear Him; His commandments you shall observe, and to His voice you shall hearken; Him you shall serve and to Him you shall cleave?"
I believe that Moses wanted to spell out the various elements which comprise serving the Lord. Once we know this we can better understand why the penalty for a false prophet or a dreamer applies even if he asks you to violate only a single one of these elements which are part of serving God by applying them to worship of an alien deity. The first element in serving the Lord, i.e. "following Him" is the acceptance of the yoke of Heaven and not the dictates of any other power claiming to be a god. This teaches us that if the prophet asks the people to accept the sovereignty of any other power he is guilty of enticing the people to serve idols. Moses was careful to use the word תלכו, "you shall walk (future)," to teach us that even if said prophet did not demand immediate acceptance of an alien deity he is still guilty of the death penalty from the moment he made such a statement.
Moses continues: ואותו תיראו, "and Him you shall fear," to emphasize that only Him you shall fear. You must not be afraid of any other so-called power in this universe. The Torah implies that even if the false prophet does not suggest you worship or sacrifice to any other power but only "fear" it, he has thereby become guilty of the death penalty. One must only fear God in Heaven.
Moses continues: ואת מצותיו תשמרו, "and His commandments you shall observe," i.e. His commandments and not the demands made in the name of any other deity. The new element in this statement is that if, say, the deity orders you to do something which brings in its wake a tangible benefit, such as the promise that if you perform a certain act you will become rich as a result, then although the act itself has no connotation of worship you must not do it as you must not take orders from anyone but God. If the false prophet were to say that God has ordered him that the people should perform a certain idolatrous act in order to be successful, such a false prophet is liable to execution.
Moses goes on to say ובקולו תשמעו, "and you shall hearken to His voice," to remind you that you are to listen only to the teachings revealed in the Torah and to teach these sacred words. You are not to listen to words spoken by the Avodah Zarah. [I suppose it would be prohibited to listen to the sound of the voice of the oracle in Delphi. I was there myself, but it did not speak. Ed.] If the false prophet claims to have been instructed by God to listen to what such a deity has to say he is guilty of death even though he does not perform a deed or even fears the deity in any way.
ואותו תעבדו, "and Him you shall serve," etc. This also means "God exclusively." We can illustrate this with the story told in Gittin 57 of the Seleucid Emperor who said to Hannah's youngest son that he should merely pretend to throw the ring on his finger in front of the idol and he could then come and bring it back so that the onlookers would gain the impression that he had performed an act of obeisance though in his heart he had not meant to do this at all. The son refused and was killed for refusing. The Torah tells us here that if a false prophet were to come and tell such a son of Hannah in the name of God that he could do what the Emperor requested of him, such a prophet would make himself guilty of the death penalty [though all he wanted was to save the boys' life. Ed.].
ובו תדבקון, "and you are to cleave to Him. This expression may be understood in conjunction with Ketuvot 111 where the Talmud asks how it is possible for man who is made of matter to cleave to God who is totally abstract? The answer given is that we are to cleave to Torah scholars as they are the carriers of the Shechinah, the presence of God. By cleaving to Torah scholars one is considered as having attached onself to God. ובא האות והמופת לאמור נלכה אחרי אלוהים אחרים, "and the sign or the wonder comes about, of which he spoke to you saying: 'Let us follow gods of others, etc.'" Moses does not quote the false prophet as saying: "let us serve the gods of others" in order to teach us that he is guilty of the death penalty even without encouraging the Israelites to "serve" those gods. Even though Moses concludes the verse with the prophet saying: "and let us worship them," Moses merely means that in the end at one point or another such a false prophet will ask you to worship and to serve the deity in question. This is why in the next verse (6) the Torah speaks of והנביא ההוא, "that prophet;" i.e. "this prophet" who wanted to escape execution by his devious ways will be executed, כי דבר סרה על השם, "because he has said something perverse against God." Although this prophet did not literally promote idol worship he lied vis-a-vis God by prophesying lies. The Torah makes it plain that a true prophet would never predict such things, much less in the name of the Lord. Any command by an established prophet for the Jews to temporarily violate one of the commandments is valid only for one of the commandments not involving idolatry. With regards to idolatry the slightest deviation is taboo and God will not even tolerate a minute deviation in an emergency. Sifri confirmed what we have said by translating the word סרה, as "falsified." Committing fraud with the Torah is a capital sin.
Apart from the approach we have taken to explain our verse, i.e. that it is intended to address the six elements involved in serving God, one may also view Moses as alluding to the six major sections of the oral Torah, i.e. the Mishnah. The words: "follow the Lord your God" refer to the section called Zeraim. This section contains laws involving the gleaning after the farmers have harvested their grain or orchards, as well as many laws designed to cater to the needs of the poor. It therefore reflects the attributes of God who cares for the needy. It also contains a tractate about the need to bring one's second tithe all the way to Jerusalem to consume it or its equivalent in that city. There is also a story Shemot Rabbah 31 about a farmer who had duly discharged all the various commandments dealing with tithes and gifts to the Levite, the priest and the poor, and who found that the normal yield of his field amounted to one thousand bushels. After a while the farmer died and during the year following the father's death the field continued to yield its regular harvest. The son, who was miserly, separated less than the required amount of tithes, and found to his distress that in the following year the yield of the field declined by approximately the amount he had thought he had saved by cutting back on his tithes, etc. He continued to deprive the Levite and the poor of even more of their due only to find that the harvest of his field kept shrinking apace. The story proves that the earth's produce is in direct proportion to whether the farmer fulfills his social obligations laid down in the Torah. This is what Moses alluded to when he instructed the Israelites: אחרי ה' אלוהיכם תלכו, "follow after the Lord your God!"
Another nuance in the wording of this verse which suggests that it may allude to laws in the section Zeraim of the Mishnah, is that that section relates to laws governing man's nourishment and his food supply. Maimonides writes in his treatise Hilchot Deyot 3,2 that when man eats and drinks he has to concentrate on the thought that the purpose of eating and drinking is to keep his body in good health so that he can serve the Lord with all his strength. He bases this on Proverbs 3,6: "Acknowledge Him in all your ways (activities)." This is what Moses meant when he wrote אחרי ה'... תלכו, "i. e. in your ways, your activities.
ואותו תיראו, "and Him you shall fear." This is an allusion to the second section of the Mishnah, the one called Moed which deals with all the festivals and the Sabbath. The word אתו is an allusion to the Sabbath which is called אות in Exodus 31,17. Festivals are also described in the Torah as אות, "sign." The author of Tikkuney Hazohar chapter 9 relates to that fact by saying that just as one needs to fear violating the Sabbath one should fear violating the laws pertaining to the festivals.
ואת מצותיו תשמרו, "and observe His commandments." This is an allusion to the section of the Mishnah called Nashim in which the many laws concerning marriage, forbidden unions, family purity, etc., are discussed.
ובקלו תשמעו, and to His voice you shall hearken; this is an allusion to the various tractates dealing with property rights called Nezikin. One needs to pay careful attention to the judges who render judgment in matters of civil disputes. One must not depart fom what the judges rule, as spelled out in Deut. 17,12 "any man who deliberately fails to obey the ruling by the priest, etc.
ואתו תעבדו, "and (only) Him you must serve." This is an allusion to the section called Kodoshin. It deals with the details of the Temple Service, etc.
ובו תדבקון, and to Him you shall cleave." This is an allusion to the sixth and final section of the oral Torah which deals with matters of ritual purity. By observing these laws in its details one becomes worthy of cleaving to the Shechinah, the presence of God.