The Midrash in Parshas Noach comments on the pasuk "Vayarach Hashem es rei'ach ha'nicho'ach" that Hashem was smelling not just the fragrant odor of Noach's korban, but was also smelling Avraham in the furnace of Nimrod, he was smelling Chananya, Mishael, v'Azarya in their oven, he was smelling the sweet scent of all those who sacrifice their lives al kiddush Hashem.
When you walk through the front door of your home on Friday afternoon, you know what is cooking and your mouth begins to water even before you see the food on the stove, hear the clanging of pots and silverware, or even get to the kitchen. The aroma and smell of Shabbos food beckons and causes us to anticipate the meal ahead, the Shabbos ahead. Similarly, even though Avraham hadn't come on the scene yet, Chananya, Mishael and Azarya were in the distant future, as was the sacrifice of so many others, Hashem already "smelled" and anticipated what was coming. That whiff the future proved that there was hope for mankind.
Rosh Chodesh too is a holiday of smell, of anticipation. The Shem m'Shmuel (Noach 5675) writes that the letters of the word for moon, "yareiach" = yud, reish, cheis, are the same letters as "rei'ach"=reish, yud, cheis. Rosh Chodesh comes when the moon is just a sliver, but we look forward to the day when we sill see "ohr ha'levanah k'ohr hachamah." We say in Kiddush hachodesh, "David melech yisrael chai v'kayam," in anticipation of the restoration of malchus beis David. We're not there yet, but we celebrate because we "smell" what is coming.
The gemara (Eiruvin 21) interprets Yirmiyahu's vision (ch 24) of two pots of figs, one of good figs, one of bad ones, as symbolic of tzadikim and evildoers. Perhaps, says the gemara, these rotten figs are have no value and should be tossed in the trash? The gemara responds by quoting the pasuk, "Hadudaim nasnu rei'ach," (Shir haShirim 7)interpreting "dudaim" not as mandrakes, but as the dud, the pot, of rotting figs. That pot too will give off a sweet smell. That pot may not look like much now, but Hashem smells, Hashem anticipates, and he detects a brighter future.
When I saw this Shem m'Shmuel back in Parshas Noach I put it in the back of my mind to post now because I can't understand why he didn't tie it into our parsha. Yitzchak smells the odor of Eisav's garments, "Va'yarach es rei'ach begadav." Chazal read it not as "begadav," Eisav's clothes, but "bogdav," those who rebel against Hashem. "Re'ei rei'ach b'ni k'rei'ach sadeh asher beiracho Hashem" -- Yitzchak remarks that he smells a field blessed by G-d. Yitzchak doesn't see rebellion; he smells bracha. Perhaps his loss of sight allowed Yitzchak to focus on and anticipate the future instead of dwelling only on the here and now before him, to smell instead of just seeing, and as a result, those "bogdav," rebels, he knew would turn out to be blessed as well.