Shavuot תרמ"ה 6

איתא בעשרה מאמרות נברא העולם ומה ת"ל כדי ליתן שכר כו'.

It is brought: "With ten utterances (asarah maamaros) the world was created. And what does this come to teach? [Could it not have been created with a single utterance?] — rather, in order to give reward [to the righteous who sustain the world... and to exact punishment from the wicked who destroy it]" (Avos 5:1).

The Mishnah asks why Hashem created the world through ten separate utterances when one would have sufficed. Its answer: to make each part of creation count, so that the righteous earn greater reward for sustaining a world built with so much "speech," and the wicked bear greater accountability for harming it.

וכמו כן יתכן לומר כי בודאי גם עשרת הדיברות בדיבור אחד הי' יכול לכלול הכל וכמ"ש רש"י שהי' בכלל ואח"כ בפרט רק שגם בתורה נשאר מדריגות ליתן שכר לעוסקים לשמה ולהפרע מעוסקים לקנתר כו' וכמ"ש סמא דחיי למיימינים בה כו':

And likewise it may be said that surely the Aseres HaDibros (Ten Commandments) too could have included everything in a single utterance — as Rashi writes that it was [stated] in general and afterward in detail — only that in the Torah as well there remain gradations, in order to give reward to those who study it lishmah (for its own sake) and to exact payment from those who study it in order to provoke (l'kanter), etc. As it is written: "It is a potion of life for those who go to its right…[and a potion of death for those who go to its left]" (Shabbos 88b).

Just as the world could have been made with one utterance but was deliberately given ten, so too the Torah could have been given as one all-inclusive statement (and indeed Rashi notes the Dibros were stated first in general, then in detail). The reason it unfolds in many distinct levels and details is the same: so that those who learn Torah lishmah earn reward through each part, while those who approach it with the wrong motive — to provoke and quarrel — are held accountable. The same Torah is a life-giving elixir for those who approach it rightly and the opposite for those who do not.

Summary: Just as the world was created through ten utterances rather than one — to grant greater reward to those who sustain it and greater accountability to those who harm it — so too the Torah, though it could have been given as a single all-encompassing statement, was given in distinct levels and details. This is so that those who study Torah lishmah earn reward, while those who study it to provoke bear consequence: the same Torah is an elixir of life or its opposite, depending on how one approaches it.