Reference for Avodah Zarah 94:18

דמהו דתימא כיון שסייד וכייד בגופה של אבן כאבן שחצבה מתחלה לעבודת כוכבים דמיא ותיתסר כולה קמ"ל:

For what might you have said? Since he plastered and tiled in the material of the stone, it is analogous to a stone which had been originally hewn for idolatry and the whole of it is prohibited. Therefore he teaches us [that it is not so].

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