Why these specific parts? The breast and shoulder carried profound symbolic meaning pointing beyond the physical.
The 'wave breast' and 'heave shoulder' were not just random cuts of meat. The breast, where the heart is, traditionally symbolized wisdom, thought, and emotion. The shoulder represented strength and the ability to act. When these parts were 'waved' (symbolizing God's sovereignty over the whole earth) and 'heaved' (symbolizing God's elevation to heaven), they pointed to the ideal qualities of service. These were meant to remind the priests, and ultimately us, that true service to God requires wisdom and strength, reflecting the very nature of Christ, our ultimate High Priest.