Reference for Ketubot 144:13

רב אשי אמר לעולם ארישא ומידי דקפדי בה אינשי הוה קפידיה קפידא מידי דלא קפדי בה אינשי לא הוי קפידיה קפידא

R. Ashi said: It may in fact refer to the first clause, but in respect of the vows to which people usually take exception his objection is valid. In respect of vows to which people do not as a rule take exception his objection has no validity.

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