The Forbidden Work of Reaping in the Mishkan
The Mishnah (Shabbat 73a) states that one of the forbidden works on Shabbat is reaping. All works forbidden on Shabbat were performed while erecting the Mishkan. Reaping was necessary in the Mishkan’s construction, for the fabrics of the Mishkan were colored with various dyes produced from plant and herb derivatives. Thus, one who harvests something from the ground is liable for Shabbat desecration.
What is the Forbidden Work of Reaping?
Included in the forbidden work of reaping is reaping wheat or barley, picking grapes, olives, dates, or figs (off the tree or vine) or anything else that grows from the earth. Nevertheless, once a branch is detached from the earth, although there are fruits on it, these fruits may be picked on Shabbat, for these fruits are no longer attached to the ground. It is therefore permissible to pick grapes from their cluster on Shabbat, since the cluster is no longer attached to the ground.
Smelling Something Attached to the Ground
The Gemara in Masechet Sukkah (37b) states: “Rabba said: One may smell a myrtle branch attached to the ground but not an Etrog (citron) attached to the ground. The reason for this is because a myrtle branch is made for smelling and by permitting this, one will not come to detach it. An Etrog, on the other hand, is made for eating and therefore, if we permit smelling it, one will come to detach it.” This means that a myrtle branch or any other fragrant plant may be smelled on Shabbat, even when it is still attached to the ground, for since it is designated only for smelling and not for eating, there is no concern that one will detach it from the ground since it can be smelled while still attached. However, regarding an Etrog or any other fruit which has a pleasant smell, it is forbidden to smell it while it is still attached to the tree, for since it is primarily designated for eating, we are concerned that when one smells it, one will want to eat it as well and detach it from the ground on Shabbat.
It is therefore forbidden to smell a fruit tree which gives off a fragrant scent on Shabbat; however, smelling a tree which does not have fruit but nevertheless gives off a fragrant scent is permissible on Shabbat. Maran Harav Ovadia Yosef zt”l writes that when smelling an attached myrtle branch on Shabbat, one may even grasp it in order to smell it and it is not Muktzeh; one should, nevertheless, take care not to detach even a small amount of the leaves on Shabbat.
One should take special care when smelling fragrant plants, such as myrtle and rosemary branches, not to detach any leaves when rubbing the leaves together in order to bring out the scent, for this is indeed a transgression of Torah law.