The Pharisees had this idea setting money aside for God, and it could then no longer be used to look after elderly parents. But this money was still in their possession! It was a legal way of evading the command to care for parents, while looking pious at the same time. We are all susceptible, wanting to look like we're doing the right thing. External religion is much easier than dealing with the problems of our heart. We feel ourselves to be false and full of sin but there is grace to cover all our sin.