Where does the phrase, "Give lip service" come from? Here is one of the most ancient sources: Isaiah. I'll show you what Isaiah is talking about, and you can see if it still applies today.
The context is a "Woe Oracle" to Judah for their sins. What were their sins? A few examples: they went out of their way to hide their plans from God. They felt Yahweh had no say in certain parts of their lives. Yahweh pronounces "woe" or judgment on those who try to hide sin from God, saying, "Who sees us? Who will know?"
Another sin is making God to be what we want Him to be. Yahweh is calling them out for reversing the natural order of God being the potter and Judah the clay. "Shall what is formed say to him who formed it, 'He did not make me'?" They had "turned things upside down as if the potter were thought to be like the clay!"
Finally, they gave lip service. They acted like they knew God, worshiped him, went to make offerings, but God knew their hearts were not loving toward God, toward fellow man, were far from Yahweh. That's why Yahweh says, "They honor me with their lips, but their hearts are far from me."
Now, let's look at Jesus in Mark 7:1-23. Jesus directly quotes the prophet Isaiah, even affirms Isaiah was right not only in describing the situation in Judah in the 700s B.C. but his words would also be true in Jesus' day. Jesus criticized the Pharisees because they were so upset about his disciples "eating with unclean hands." The Pharisees had lots of extra laws they worried about related to ceremonial washings, cleaning cups and bowls. They were washing off any "unclean" thing they'd touched in the marketplace, any Gentilian thing -- eyew!
Jesus' point was not that washing was necessarily bad, but that they had so focused on these laws that they had neglected the weightier matters of the law: justice, mercy, love. For example, Jesus quoted the fifth commandment to honor father and mother, but the Pharisees had made up a loophole, and it went something like the following.
If my parents are in need, fine, but I can give my gift to God in the temple in place of helping my parents, and I can get a "two-fer," both giving to God and giving what I would otherwise give to my parents to God. You know, it's kind of like when someone gives a gift to a charity and sends you a card in the mail saying, "I gave a gift to [charity] in your honor." They got to give to their favorite charity and "give" you a gift as well!
That's how Pharisaic Corban works, and it's still at work today in the lives of Christians. It's called Lip Service, Corban, and Jesus still believes you and me need to discipline our lips and hearts to come together in our honor for the Lord of Heaven and Earth.
Pray in private without telling someone you are praying for them.
Fast without telling anyone.
Give to someone without anyone finding out, even the person you give to.