What do we learn from "Ki Na'im Ki Sishmerem b'Vitnecha [Yikonu Yachdav Al Sefasecha]"?
Eruvin 54a: Divrei Torah are pleasant when one guards them in his stomach (remembers them), i.e. when "Yikonu Yachdav Al Sefasecha" (Rashi here - he says the words audibly).
Sanhedrin 99b 1 : All bodies were created to toil. Happy are those who toil in Torah.
Rashi: It will be pleasant for you afterwards if you guard them and hide them in your stomach, lest you forget them.
R. Yonah: Guard them, lest they veer from your heart, and so you will fulfill them in practice.
Malbim: After you accepted Divrei Chachamim, Daiti is good for you, i.e. what I gave Meshalim and taught to you Chachmah according to Da'as; via this, you can say them with your lips. The lips denote Da'as - something known clearly, that one can speak and tell its Emes with his lips. This is a great level! If you guard them in your stomach, they are Na'im v'Nadim (transient); you do not know them with Da'as, just guard them like you received them. They are not fixed in you like nails that do not budge.
This is based on Dikdukei Sofeim and Margoliyos ha'Yam, who re-arrange the text. (PF)
Why does it say "Yikonu Yachdav Al Sefasecha"?
R. Yonah: Prepare them on your lips, lest you forget them in practice. The expression of Chachmah is always on the lips. When the words are fluent on the tongue - this causes remembrance.
Malbim: When they are prepared together on your lips - they left your stomach to your lips, to express them with lips of Da'as, then they are founded. They do not wander; they find a base and will not depart from their place.
