וּנְתָֽנְךָ֨ יְהוָ֤ה לְרֹאשׁ֙ וְלֹ֣א לְזָנָ֔ב וְהָיִ֙יתָ֙ רַ֣ק לְמַ֔עְלָה וְלֹ֥א תִהְיֶ֖ה לְמָ֑טָּה כִּֽי־תִשְׁמַ֞ע אֶל־מִצְוֺ֣ת ׀ יְהוָ֣ה אֱלֹהֶ֗יךָ אֲשֶׁ֨ר אָנֹכִ֧י מְצַוְּךָ֛ הַיּ֖וֹם לִשְׁמֹ֥ר וְלַעֲשֽׂוֹת׃
Yehovah te colocará como cabeça e não como cauda; e estarás somente por cima, e não estarás por baixo, pois darás ouvidos aos mandamentos de Yehovah, teu Elohim, que hoje te ordeno, para guardar e cumprir.
Or HaChaim
יפתח ה׳ לך את אוצרו הטוב, "G'd will open for you His store of goodness, etc." From this point on until the end of verse 13 the Torah describes the reward for fulfilling the positive commandments. This is why verse 13 concludes with the words "if you listen to the commandments of the Lord your G'd." The channels which G'd employs to direct the outpourings of His goodness to earth are activated through performance of commandments rather than through the passive refraining from violating negative commandments.
Ramban
AND THOU SHALT NOT TURN ASIDE FROM ANY OF THE WORDS WHICH I COMMAND YOU THIS DAY. This is connected with the expression [in the preceding Verse 13] if thou shalt hearken, meaning that all these blessings will come upon you when you will hearken to His commandments, and when you will not turn aside to the right, or to the left85In Verse 14 before us. from any of the words which I command you concerning idolatry. For, if you will go after other gods to serve them85In Verse 14 before us. you will already have turned aside from all His commandments86See Ramban to Numbers 15:22. — The verse before us, And thou shalt not turn aside from any of the words which I command you this day, is thus not an independent negative commandment, as the author of the “Hilchoth Gedoloth” would have it, but is rather to be understood in connection with the concluding part of that verse, to go after other gods to serve them, meaning to say: if you will go after other gods to serve them, you will already have turned aside from any of the words which, command you this day. and He shall have no desire whatever for any of the commandments you may observe. The sense of the verse is thus unlike the words of the “Hilchoth Gedoloth”59Rabbi Shimon Kairo of the Gaonic period, who flourished in the second half of the eighth century Common Era, was the first to enumerate the Taryag Mitzvoth contained in the Torah. The listing is in the preface to his work “Hilchoth Gedoloth”. His concept was utilized by the Paitanim, the writers of liturgical poetry who wrote various Azharoth (Exhortations), liturgical poems containing the Divine Commandments. — It should be noted that while the “Hilchoth Gedoloth” contains the first historical record in our possession of an attempt at enumerating the individual commandments, there is no doubt that the author drew upon older sources of such lists, and as Rabbeinu Saadia Gaon writes here, such “a list of the commandments” was written upon the stones by Moses. who counted this verse as a negative commandment.
Chizkuni
ולתתן עליון, “and to place you supreme;” where is the source for G-d doing this? Compare Deut. 28,13: 'ונתנך ה לראש ולא לזנב, “and the Lord will make you the head and not the tail.”