Exodus 7:14 Yahweh said to Moses, "Pharaoh's heart is stubborn. He refuses to let the people go. (See NIV)
Exodus 9:7 Pharaoh sent, and, behold, there was not so much as one of the livestock of the Israelites dead. But the heart of Pharaoh was stubborn, and he didn't let the people go. (See NIV)
Proverbs 18:19 A brother wounded is like a strong town, and violent acts are like a locked tower. (See NIV)
Song of Songs 8:6 Put me as a sign on your heart, as a sign on your arm; love is strong as death, and wrath bitter as the underworld: its coals are coals of fire; violent are its flames. (See NIV)