Definition and Purpose:
Fasting, in the biblical context, is the voluntary abstention from food, and sometimes drink, for a specified period. It is a spiritual discipline intended to humble oneself before God, seek His guidance, express repentance, or prepare for a significant spiritual endeavor. Fasting is often accompanied by prayer and is seen as a means to draw closer to God, demonstrating dependence on Him rather than on physical sustenance.

Old Testament Context:
Fasting is a well-documented practice in the Old Testament, often associated with mourning, repentance, and seeking divine intervention. One of the earliest mentions is in the context of the Day of Atonement, a national fast day for Israel (Leviticus 16:29-31). The prophet Joel calls for a fast as a response to a locust plague, urging the people to "return to Me with all your heart, with fasting, weeping, and mourning" (Joel 2:12).

Fasting is also seen in the lives of individuals. King David fasted and prayed for the life of his child (2 Samuel 12:16), and Queen Esther called for a fast among the Jews before she approached the king to plead for her people (Esther 4:16). The prophet Daniel engaged in a partial fast, abstaining from choice foods, as he sought understanding and revelation from God (Daniel 10:2-3).

New Testament Context:
In the New Testament, fasting continues to be a significant spiritual practice. Jesus Himself fasted for forty days and nights in the wilderness before beginning His public ministry (Matthew 4:2). He taught about fasting in the Sermon on the Mount, instructing His followers to fast discreetly and not for the sake of public recognition: "When you fast, do not be somber like the hypocrites... But when you fast, anoint your head and wash your face" (Matthew 6:16-17).

The early church practiced fasting as part of their worship and decision-making processes. In Acts 13:2-3, the church in Antioch fasted and prayed before sending out Paul and Barnabas on their missionary journey. Similarly, in Acts 14:23, fasting accompanied the appointment of elders in the churches.

Theological Significance:
Fasting is seen as an act of humility and submission to God. It is a physical expression of a spiritual reality, acknowledging human frailty and dependence on God. Fasting is not a means to manipulate God but a way to align oneself with His will and purposes. It is often associated with repentance, as seen in the account of Nineveh, where the people fasted and turned from their evil ways, prompting God to relent from sending disaster (Jonah 3:5-10).

Practical Considerations:
While fasting is a powerful spiritual discipline, it should be approached with wisdom and discernment. Individuals with health concerns should consult with medical professionals before undertaking a fast. The focus of fasting should remain on seeking God and His righteousness, rather than on the act of fasting itself.

Conclusion:
Fasting remains a relevant and meaningful practice for believers today, offering a way to deepen one's relationship with God, seek His guidance, and express sincere repentance. Through fasting, believers can experience spiritual renewal and a greater sensitivity to the leading of the Holy Spirit.