Definition and Nature:
Hard-heartedness, in biblical terms, refers to a spiritual condition characterized by an unyielding, stubborn, and unresponsive heart towards God and His commandments. It is often associated with a refusal to listen, repent, or obey, leading to a separation from God's will and purpose.

Biblical Examples:

1. Pharaoh of Egypt:
One of the most prominent examples of hard-heartedness is Pharaoh during the Exodus narrative. Despite witnessing numerous signs and wonders performed by God through Moses, Pharaoh repeatedly hardened his heart, refusing to let the Israelites go. The Bible states, "But Pharaoh's heart was hardened, and he would not listen to them, just as the LORD had said" (Exodus 7:13). This obstinacy led to severe plagues upon Egypt, culminating in the death of the firstborn and the eventual destruction of Pharaoh's army in the Red Sea.

2. The Israelites in the Wilderness:
The Israelites, after being delivered from Egypt, displayed hard-heartedness during their journey in the wilderness. Despite God's continuous provision and guidance, they grumbled and rebelled against Him. Psalm 95:8-9 warns, "Do not harden your hearts as you did at Meribah, as you did that day at Massah in the wilderness, where your fathers tested and tried Me, though they had seen My work." Their hard-heartedness resulted in a prolonged journey and the denial of entry into the Promised Land for that generation.

3. The Religious Leaders of Jesus' Time:
The Pharisees and Sadducees often exhibited hard-heartedness towards Jesus and His teachings. Despite witnessing His miracles and hearing His wisdom, they refused to accept Him as the Messiah. Mark 3:5 describes Jesus' reaction: "And He looked around at them with anger, grieved by their hardness of heart." Their resistance ultimately led to their role in His crucifixion.

Spiritual Consequences:

1. Separation from God:
Hard-heartedness creates a barrier between individuals and God, leading to spiritual blindness and deafness. Isaiah 6:10 illustrates this, "Make the hearts of this people calloused; deafen their ears and close their eyes. Otherwise they might see with their eyes, hear with their ears, understand with their hearts, and turn and be healed."

2. Judgment and Discipline:
Persistent hard-heartedness invites God's judgment and discipline. Romans 2:5 warns, "But because of your hard and unrepentant heart, you are storing up wrath against yourself for the day of wrath, when God’s righteous judgment will be revealed."

3. Loss of Blessings:
A hard heart can lead to the forfeiture of God's blessings and promises. Hebrews 3:12-13 cautions believers, "See to it, brothers, that none of you has a wicked heart of unbelief that turns away from the living God. But exhort one another daily, as long as it is called today, so that none of you may be hardened by sin’s deceitfulness."

Remedy and Prevention:

1. Repentance and Humility:
The Bible calls for repentance and humility as remedies for hard-heartedness. Ezekiel 36:26 promises, "I will give you a new heart and put a new spirit within you; I will remove your heart of stone and give you a heart of flesh."

2. Obedience to God's Word:
Regular engagement with Scripture and obedience to God's commands can prevent the hardening of the heart. Psalm 119:11 states, "I have hidden Your word in my heart that I might not sin against You."

3. Prayer and Fellowship:
Maintaining a prayerful life and fellowship with other believers can soften the heart and keep it receptive to God's voice. Hebrews 10:24-25 encourages believers to "spur one another on to love and good deeds" and not to forsake gathering together.

In summary, hard-heartedness is a serious spiritual condition with significant consequences, both temporal and eternal. The Bible provides numerous examples and warnings, urging believers to remain vigilant, humble, and obedient to avoid the pitfalls of a hardened heart.