One Sabbath he was going through the grainfields, and as they made their way, his disciples began to pluck heads of grain. And the Pharisees were saying to him, “Look, why are they doing what is not lawful on the Sabbath?”
Mark 2: 23-24 ESV
Another day, another complain from the pharisees. God gave the Israelite the commandment to celebrate the Sabbath as the rest day in the seventh day. It’s purpose was that the people of God will have that special time to have fellowship with God. It’s a consecrated day for the people of God. However the Pharisees made lots extra rules and made the observance legalistic. That even plucking heads of grain is considered breaking the law of Sabbath.