Woe to you who swallow camels: The passage forms the fourth and fifth of a series of “woes” addressed to the scribes and Pharisees.
The fourth woe, an expression of a speaker’s horror concerning sin and a proclamation of the punishment awaiting those who sin, contrasts things of lesser importance (tithes on herbs) with things of great importance (justice, mercy, and faithfulness) for Matthew. The scribes and Pharisees were preoccupied with trivial matters. The real issue, as Matthew presents it, is not whether one should pay tithes but the weightier things of the law.
The fifth woe consists of a comparison between a cup and a person. Just as there is an inside and an outside to a cup, so is there an inner disposition and an outer disposition to a person.
The scribes and Pharisees are accused of observing the ritual washing of the outside of the cup but never cleansing the inside of it. Their appearances are pleasing (they look good), but their hearts are ready to rob anyone: they have no self control.
Inner purity is not accomplished by outer washing. A person must clean up his or her inner dispositions first. Authenticity flows from the “within” to the “without” and vice versa. Inner cleansing makes the whole person clean.
As is typical of Matthew, the issue remains the right behavior, the conduct that God wants, righteousness. Members of the Matthean church are being warned to be authentic, to possess an inner and outer harmony. God is not interested in appearances; God is interested in the heart.