פירוש על עבודה זרה 93:7

R. Dimi says that the question was asked with regard to an asherah, a tree that had been planted to be worshipped that was then annulled. The concept of “disqualification” is that once an object has been disqualified it cannot go back and become qualified again. If we apply this concept to the lulav, then since the lulav could not have been used when the tree was still an asherah, it cannot be used later when the tree is no longer an asherah.