Definition and Context:
Boasting about tomorrow refers to the act of making presumptuous claims or plans about the future without acknowledging the sovereignty and will of God. This concept is addressed in the Bible, particularly in the context of human pride and the uncertainty of life. It serves as a caution against self-reliance and a reminder of the need for humility and dependence on God.

Biblical References:
The primary scriptural reference for boasting about tomorrow is found in the Book of James. James 4:13-16 states: "Come now, you who say, 'Today or tomorrow we will go to this or that city, spend a year there, carry on business, and make a profit.' You do not even know what will happen tomorrow! What is your life? You are a mist that appears for a little while and then vanishes. Instead, you ought to say, 'If the Lord is willing, we will live and do this or that.' As it is, you boast in your proud intentions. All such boasting is evil."

Theological Implications:
The passage in James highlights the transient nature of human life and the folly of making plans without considering God's will. It underscores the belief that God is sovereign over all aspects of life, including the future. By acknowledging "If the Lord is willing," believers are encouraged to submit their plans to God's authority, recognizing that He alone knows and controls the future.

Related Concepts:
1. Humility: Boasting about tomorrow is contrasted with the biblical virtue of humility. Proverbs 27:1 advises, "Do not boast about tomorrow, for you do not know what a day may bring." This verse emphasizes the importance of humility in acknowledging human limitations and the unpredictability of life.

2. Dependence on God: The act of boasting about tomorrow reflects a misplaced confidence in one's own abilities and understanding. Instead, Scripture calls believers to trust in God's provision and guidance. Proverbs 3:5-6 instructs, "Trust in the LORD with all your heart, and lean not on your own understanding; in all your ways acknowledge Him, and He will make your paths straight."

3. The Brevity of Life: The metaphor of life as a "mist" in James 4:14 serves as a reminder of life's brevity and the urgency of living in accordance with God's will. This perspective encourages believers to focus on eternal values rather than temporal achievements.

Practical Application:
Believers are encouraged to approach their plans and ambitions with a heart of submission to God. This involves seeking His guidance through prayer, studying His Word, and being open to His leading. By doing so, Christians can align their desires with God's purposes and live with a sense of peace and assurance, knowing that their future is in His hands.

Warnings Against Pride:
The Bible consistently warns against the dangers of pride and self-sufficiency. In Luke 12:16-21, Jesus tells the parable of the rich fool who stored up earthly wealth without regard for his soul's eternal state. The man's sudden death serves as a stark warning against placing confidence in material security and neglecting one's relationship with God.

Conclusion:
While the Bible encourages planning and diligence, it also calls for a posture of humility and dependence on God. Boasting about tomorrow is ultimately a reflection of human pride, which is contrary to the biblical call to trust in the Lord and acknowledge His sovereignty over all aspects of life.