Jamieson, Fausset and Brown on Genesis 33:4

4. Esau ran to meet him--What a sudden and surprising change! Whether the sight of the princely present and the profound homage of Jacob had produced this effect, or it proceeded from the impulsive character of Esau, the cherished enmity of twenty years in a moment disappeared; the weapons of war were laid aside, and the warmest tokens of mutual affection reciprocated between the brothers. But doubtless, the efficient cause was the secret, subduing influence of grace (Pr 21:1), which converted Esau from an enemy into a friend.