Nedarim, Chapter 7, Mishnah 3. In this mishnah we deal with someone who takes a vow forbidding himself clothing, and with the question of which types of coverings are included in the wording of his vow and which are not.
"HaNoder min hakesus - mutar b'sak, biyri'ah uv'chamilah":
One who vows against "kesus", that is, against a covering of the type of a garment, is permitted to cover himself with sackcloth, with a yeri'ah, or with a chamilah. A yeri'ah and a chamilah are two kinds of very coarse, thick coverings. These are not the sort of things a person normally wears, but only under unusual circumstances, such as when someone covers himself with them against harsh weather. Since they are not ordinary garments, they are not included in the term "kesus".
One who vows against wool and against linen:
"Konam tzemer oleh alai" - one who vows that no wool shall come upon him is permitted to cover himself with fleeces of wool. Shorn fleeces are not included in the vow, since when he said "wool" he meant an actual wool garment, and not the fleeces of the flock as they are.
"Konam pishtan oleh alai" - the same applies to one who vows that no linen shall come upon him: he is permitted to cover himself with stalks of flax, that is, with the flax fibers, since his true intention was a linen garment.
"Rabbi Yehudah omer: hakol lefi hanoder":
Rabbi Yehudah rules that the matter depends on the context: everything is determined by the person taking the vow and by the circumstances he was in at the time he made it.
The mishnah brings an example: a person was carrying a load of wool or of linen, "v'hizia v'reicho kasheh" - he was dripping with sweat and it was unbearable for him. Because of this he said: "Konam tzemer ufishtim olim alai", vowing that no wool or linen should come upon him.
In such a context the mishnah teaches:
"Mutar l'hiskasos" - he is permitted to wear woolen garments and linen garments.
"V'asur l'hafshil l'achorav" - he is forbidden to place them on his back and carry them as a load, since from the context it is clear that what was unbearable for him was carrying the load, and not wearing the finished products made from these materials.
In summary: in this mishnah we learned that the wording of a vow is measured according to its ordinary meaning. One who vows against "kesus" is permitted sackcloth, a yeri'ah and a chamilah, which are not normal wearing garments, and one who vows against wool or linen is permitted fleeces of wool and stalks of flax, since he meant the finished garment. According to Rabbi Yehudah, "everything is according to the one who vows": a person who took his vow out of the difficulty of carrying a load is permitted to wear the material, but forbidden to sling it over his back.