Isaiah 1:10, 16-20 / Matthew 23:1-12
The cities of Sodom and Gomorrah were mentioned in the book of Genesis and they were destroyed by fire and brimstone because of their unrepentant sin and evil deeds.
At the time of the prophet Isaiah, those two cities were already non-existent.
Yet they were mentioned by Isaiah because the people's sins were synonymous with the sins of those two cities.
Hence Isaiah urged the people to wash themselves clean and to repent.
The direction of conversion and repentance is plain and simple - cease to do evil, learn to do good, search for justice, help the oppressed, be just to the orphan, plead for the widow.
It is as plain and simple as that. No need for big show like wearing broader phylacteries and longer tassels and doing things just to attract attention and to give people a false impression.
Yet plain and simple as it may be, to turn from evil and learn to do good, to be just and help the oppressed demands that we be humble and be a servant to the poor and the needy, the helpless and the oppressed.
Yes it is very difficult to be humble and be a servant of the voiceless and the faceless lowly people.
Yet it would be better to be voiceless and faceless than to be referred to as the people of Sodom and Gomorrah.