פירוש על עבודה זרה 38:12

Yirmiyah says that R. Yohanan was referring to a Jew who helped build the idol itself, not just the cupola. His pay is still permitted, despite the fact that he helped make an idol.

There is a debate about whether an idol made for an idolater becomes prohibited immediately when it is made, or only when it is worshipped. If the rule is that any benefit derived from it becomes prohibited only once it is worshipped, then R. Yohanan’s statement makes sense. The Jew made this idol for the idolater, but until the idolater actually worships it, the Jew may use the wages. But if the prohibition begins immediately, then how can the wages be permitted?