Luke 6:1 “Now it happened on the second Sabbath after the first that He went through the grainfields. And His disciples plucked the heads of grain and ate them, rubbing them in their hands.”
This was likely Shavuot, or Pentecost, at the time of the harvest of wheat. The only allowance for the gathering of the grains of wheat was made for the priests, who must make the show-bread. This immediately explains two things. First, it explains why this would be seen as wrong by the Pharisees. Second, it explains why it would be seen as right by the disciples.
Heavenly Father, thank You for the Bread from Heaven, the Lord Jesus! You have put Him above and before all things. Your wisdom and power are so complete! We stand in awe every hour. In the Name of the Lord Jesus Christ I pray and praise You, Amen.