What is the significance of descending to his garden?
Rav Sadya Gaon: The Shechinah returns to the Beis ha'Mikdash.
Rashi: He commanded us to build His Heichal, and He was there with us.
Seforno: To a congregation of Kedoshim - Anshei Keneses ha'Gedolah.
Malbim (Melitzah): Nefesh Shlomo sensed that the supreme Beloved descends from His Kadosh abode to gather it to Himself.
What is "Arugas ha'Bosem"?
Rashi: It is a place where Ketores is burned.
Malbim (Melitzah): The supreme Beloved did not descend to the entire garden (all bodily powers and Nefashos), only to the patch of fragrances - the spiritual, Divine Nefesh. One plants five kinds of seeds in a patch 1 . David said five times "Barchi Nafshi" corresponding to Hashem and the Neshamah (Brachos 10a), the supreme fragrance that ascends for a pleasant scent to Him.
Malbim (Mashal): This is his beloved - his fragrance.
Shabbos 84b: This is for a patch six by six Tefachim. There is one on each of the four sides, and one in the middle. More than this is forbidden due to Kil'ayim.
Why does it say "Lir'os ba'Ganim"?
Rashi: To graze in the gardens His flock that were scattered there - those who did not ascend from Galus, He puts His Shechinah on them in Batei Kenesiyos and Batei Midrash.
Seforno: It is to rejoice in Batei Kenesiyos and Batei Midrash - "Yismach Hashem b'Ma'asav" (Tehilim 104:31).
Malbim (Melitzah): Ganim are the saplings of the body; its vegetation grazes. I.e. via death, they will gradually be purified to return to the elements, and from there to other incarnations, until a new house will be built from them.
What is the significance of gathering roses?
Rashi: He hears and hearkens to those who speak in His Torah, to collect their merits and write them in a Sefer Zikaron in front of Him - "Az Nidberu Yir'ei Hashem
