The Revised Common Lectionary (RCL) that many churches use does not provide the casual Sunday pewsitter with a complete view of the Bible. The RCL commonly omits sections of the Bible that might be troublesome for progressive preachers to explain away or might sound offensive to modern listeners. The harm that is done is incalculable as pewsitters are taught an expurgated version of the Bible.
This Sunday is no exception. I added (in red) the verses that were cut.
Mark 7:1-8,14-15,21-23
Now when the Pharisees and some of the scribes who had come from Jerusalem gathered around him, they noticed that some of his disciples were eating with defiled hands, that is, without washing them. (For the Pharisees, and all the Jews, do not eat unless they thoroughly wash their hands, thus observing the tradition of the elders; and they do not eat anything from the market unless they wash it; and there are also many other traditions that they observe, the washing of cups, pots, and bronze kettles.) So the Pharisees and the scribes asked him, ‘Why do your disciples not live according to the tradition of the elders, but eat with defiled hands?’ He said to them, ‘Isaiah prophesied rightly about you hypocrites, as it is written,
“This people honours me with their lips,
but their hearts are far from me;
7 in vain do they worship me,
teaching human precepts as doctrines.”
8 You abandon the commandment of God and hold to human tradition.’
9 Then he said to them, ‘You have a fine way of rejecting the commandment of God in order to keep your tradition! For Moses said, “Honour your father and your mother”; and, “Whoever speaks evil of father or mother must surely die.” But you say that if anyone tells father or mother, “Whatever support you might have had from me is Corban” (that is, an offering to God)— then you no longer permit doing anything for a father or mother, thus making void the word of God through your tradition that you have handed on. And you do many things like this.’
14 Then he called the crowd again and said to them, ‘Listen to me, all of you, and understand: 15 there is nothing outside a person that by going in can defile, but the things that come out are what defile.’
17 When he had left the crowd and entered the house, his disciples asked him about the parable. 18 He said to them, ‘Then do you also fail to understand? Do you not see that whatever goes into a person from outside cannot defile, 19 since it enters, not the heart but the stomach, and goes out into the sewer?’ (Thus he declared all foods clean.) 20 And he said, ‘It is what comes out of a person that defiles.
21 For it is from within, from the human heart, that evil intentions come: fornication, theft, murder, 22 adultery, avarice, wickedness, deceit, licentiousness, envy, slander, pride, folly. 23 All these evil things come from within, and they defile a person.’
I suspect the "goes out the sewer" bit was too graphic for the editors of the RCL, but I think the other goal was to eliminate the "Thus he declared all foods clean" comment because that essentially destroys the shellfish argument.
If your church uses the RCL, you should probably find another church. If you want to stick it out, you had better open your Bible and get the whole story.