四分律行事鈔資持記 2.257

2.257

次解中。以僧尼轉根，即互入眾，更不重受。故知比丘一體具二眾戒，尼亦例爾。

In the second explanation: because when monks or nuns change sex, they enter the other assembly without undergoing reception again, we know that a bhikṣu possesses the precepts of both assemblies in a single essence, and the same is true for a nun.