Reference for Ketubot 176:2

נחלקו עליו בני כהנים גדולים ואמרו תשבע בתחלה ובסוף ר"ש כחנן רבנן כבני כהנים גדולים

The sons of the high priests differed from him and ruled that she must take an oath both at the beginning and at the end. Shimon holds like Hanan; the rabbis [hold the same view] as the sons of the High Priests.

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