Introduction:

Kneading is one of the Biblically forbidden Shabbos labors. There is a dispute dating back to the Talmud, which is likewise disputed in the codifiers, as to what constitutes kneading and as to which materials are forbidden to be kneaded. The rule is that we are stringent like all opinions.[1] It is incumbent for the learner to read the summary being that many details regarding the final Halacha are based on rulings mentioned in other places of Admur, as the current Halacha was partially omitted. The summary is based on the noted Sefer “Ketzos Hashulchan.”

Definition of Lash:

The Melacha of Lash only becomes applicable if the following conditions are fulfilled. If these conditions are not fulfilled, then the prohibition does not apply.

1. One is uniting two substances together. Mixing a single substance into itself is not defined as Lash and is permitted. See Halacha 1 Q&A regarding if mixing a single food into its natural liquid is defined as Lash [dispute] and whether mixing two pieces of the same food is defined as lash [dispute]
2. The two substances are united with each other through moisture, and stick and bond to form one item.[2]
3. Whether one of the substances must be a liquid and the second a solid, or even if both are solids or creams-see Q&A [dispute].

The three types of materials:[3]

1. Bar Gibul: Biblical material according to all.
2. Eino Bar Gibul: Biblical material according to many; Rabbinical material according to some
3. No attachment: No prohibition at all.

The three types of kneading results:[4]

1. Belila Ava: Biblical according to all.
2. Belila Raka: Rabbinical according to some.
3. Very Raka: No prohibition at all.