CUTTING HAIR AND NAILS
SEIF 1
The Gemara says regarding someone who cuts their hair and nails on Shabbos; if he does it using his hand (which is not the normal way to perform these Melachos), he is exempt from bringing a Chatos, nonetheless it is rabbinically prohibited. However, if he cuts them using a tool (without realizing that it is prohibited or that it is Shabbos), he is obligated to bring a Chatos. This Halacha is stated in the Shulchon Orech.
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