Why does he say "Mah Yafu Dodayich"?
Rashi: Every place that you showed to Me dearness, it was beautiful in My eyes - Gilgal, Shilo, Nov, Giv'on and the Beis ha'Mikdash. This is like the Paytan wrote 'Menuchah and other Ye'udim' - Menuchah is Yerushalayim, and other Ye'udim are places where the Shechinah met with Yisrael.
Seforno: In the days of Shlomo, all were Tzadikim - the king, the Kohen Gadol Tzadok, and Benyahu ben Yehoyada over the army. They are beautiful in investigation and in deed.
Malbim (Melitzah): Until now, the clinging was via prophetic understanding. The dearness was from Hashem's side. The clinging that comes via Avodah in the Mikdash is primarily from the Midah of love in Batei Nefesh. She longs for her Beloved with a strong love. It comes from below to above, via arousal of the Nefesh. Until now, He praised only her herself - "Hinei Yafah Rayasi" (1:15). Now he praises her love. Until now, He connected with her via understanding, which is the Nefesh itself. Now He connects via the flame of her love in her Avodas Hashem. Therefore He calls her Achosi - via love, she becomes His sister and equal to Him.
Why does he say "Mah Tovu Dodayich [mi'Yayin]"?
Seforno: To teach knowledge to the nation.
Malbim (Melitzah) #1: If this refers to actual wine, the Nefesh's fervor in love of Hashem exceeds its excitement over wine, which is a foreign physical fire. Ahavas Hashem is Divine and spiritual.
Malbim (Melitzah) #2: If wine is a metaphor, i.e. for an influence of Nevu'ah, her Midah of love is greater than attaining Nevu'ah. The Nefesh clings constantly in its love.
What is "Rei'ach Shemanecha"?
Rashi: Your good reputation.
Seforno: [Your good] Midos.
Malbim (Melitzah): It is the scent and understanding attained via fervor and Avodah. It is greater than all fragrances, i.e. investigative understandings. Oil poured via Ahavas Hashem is Ru'ach ha'Kodesh that clings to those who cling to Him in love.
