The Venerable Pilindavatsa was constantly afflicted with eye pain. In the course of his regular rounds begging for food, this personage always forded the River Ganges. Upon reaching the shore of the Ganges he would snap his fingers and call out, "Little slave! Stop! Don't flow!" The waters would then part and he would be free to cross and beg for food. This Ganges River spirit went to where the Buddha dwelt and addressed the Buddha, complaining, "The Buddha's disciple, Pilindavatsa, is forever insulting me, saying, 'Little slave! Stop! Don't flow!'"
The Buddha instructed Pilindavatsa to apologize to the Ganges spirit. Pilindavatsa immediately pressed his palms together and said to the Ganges spirit, "Little slave, don't be angry. I now apologize to you." At this moment, the Great Assembly laughed at this, exclaiming, "How can you apologize to her, and yet proceed to insult her once again even while doing so?!"
The Buddha said to the Ganges spirit, "As you look at Pilindavatsa, is he pressing his palms together and apologizing or not? He is apologizing without any arrogance and yet he still speaks this way. You should understand that this is not deliberate insolence. For the last five hundred lifetimes this man has repeatedly been reborn into Brahman households and thus has always been haughty and esteemed himself while slighting and demeaning others. This is just the manner of speaking which he originally practiced, that's all. In his mind there is no haughtiness."
In just this way, although the Arhats have cut off the fetters, they still retain residual traces of them.