In Matthew 18, the disciples ask Jesus who is the greatest in the Kingdom of Heaven, revealing their anticipation of a temporal kingdom and their desire for prominent positions within it. Jesus redirects their focus, teaching that entry into His Kingdom requires a profound change of heart. He emphasizes that unless they become humble like little children, they will not even enter the Kingdom, let alone be great in it. He stresses the necessity of conversion, a transformation from pride to humility, to be part of His spiritual Kingdom. Jesus further instructs that the citizens of the Kingdom must embody humility, contrasting with the disciples' ambitious pride. He warns against causing others, especially the weak or new believers, to sin, highlighting the severe consequences of such actions. Instead of striving for greatness and harming others in the process, disciples should focus on caring for Christ's little ones, the humble and trusting believers. Through the Parable of the Lost Sheep in Matthew 18, Jesus illustrates the value God places on each individual, showing that the Father seeks out and rejoices over the return of even one who strays. He teaches the disciples to mirror this care, prioritizing the weak and lost over personal ambition. The greatest in the Kingdom of Heaven, therefore, is not the one who seeks prominence, but the one who humbly serves and protects others, reflecting the Shepherd's heart.

Those whom God has delivered from the power of darkness have been conveyed into His Son's Kingdom, becoming citizens of that heavenly realm. Jesus, in His teachings, contrasts earthly and heavenly treasures, urging us to lay up treasures in heaven where they are secure, for where our treasure is, there our heart will be also. He emphasizes that no one can serve two masters, as loyalty to one means despising the other, and we cannot serve God and mammon. Jesus instructs us to seek first the kingdom of God and His righteousness, assuring us that our heavenly Father knows our needs and will provide for them. He commands us to prioritize His Kingdom above all else, though this does not mean renouncing earthly citizenship. Just as one citizenship must take precedence, our heavenly citizenship should be our master. In the heavenly Kingdom, physical distinctions such as ethnicity and earthly citizenship hold no weight, for we are all one in Christ Jesus, and His Kingdom supersedes all aspects of our earthly origins or residences. As citizens of heaven, we are merely pilgrims and sojourners on earth, passing through on our way to the Kingdom of God, observing rather than participating in the world's conflicts. Our warfare is spiritual, not physical, and we do not engage in politics, for the governments of men, though allowed by God, are in opposition to Him. We serve either the Kingdom of Heaven or the kingdoms of men, unable to serve two masters.

The Kingdom of Heaven, as emphasized by Matthew, directs our attention to its divine origins. It does not originate on the earth but in heaven, where it currently resides. Right now, the Kingdom is in heaven, not on this earth, which is why Jesus Christ is returning to reestablish the Kingdom of God here. This restoration is necessary because satan disrupted God's government on earth, necessitating a restitution of what was before. Jesus often spoke of the Kingdom of Heaven, highlighting its heavenly source and nature. It will remain in heaven until the appointed time for its restoration to earth. When Christ returns, the Kingdom of God will become both an idea and a tangible place, a literal government that exists now in heaven and will soon be established on earth. Until that time, it is not fully present here, as other preparatory steps must first be completed. The term "basileia," used in the New Testament, carries a dual meaning that confounds scholars. Primarily, it represents the rule, dominion, or sovereignty of God, encompassing anyone who submits to His rule and thus becomes part of the Kingdom of Heaven in spirit, even though it is not yet on earth. Additionally, it signifies a real government, presently in heaven, awaiting its full manifestation on earth. Jesus Himself noted that the mysteries of the Kingdom of Heaven are revealed to some, while remaining hidden to others, underscoring its spiritual discernment. God considers those who submit to Him as citizens of the Kingdom even now, in a spiritual sense. Through a legal designation, He has transferred their citizenship from this world to the Kingdom of Heaven, viewing them as ambassadors representing His rule on earth. Though still in the flesh and not yet glorified, they are hidden in Christ, covered by His righteousness, and thus remain part of the Kingdom in spirit during this training period, as they grow toward their ultimate inheritance.

The phrase "kingdom of heaven" carries multiple meanings, often understood as the coming Kingdom of God, but also referring to the physical Kingdom of Israel, established by God in heaven and governed by Him. In the Parable of the Wheat and Tares, Jesus speaks to great multitudes, explaining that the field is the world, and the good seeds are the sons of the kingdom, planted by the Son of Man. These righteous sons are revealed and glorified at the end of the age, while all who offend and practice lawlessness are gathered out of His Kingdom, which encompasses the whole world. Jesus concludes this parable by declaring that the righteous will shine forth as the sun in the kingdom of their Father. In the Parable of the Mustard Seed, Jesus addresses the condition of the physical nation of Israel, illustrating how it grew large through God's increase but fell into corruption and demonic influence, paralleling the kingdom of heaven's decline into spiritual uncleanness. Similarly, the Parable of the Leaven portrays the kingdom of heaven as like leaven hidden in three measures of meal, symbolizing the fellowship between God and Abraham's family, which over time became entirely corrupted. This indicates that the covenantal relationship within the kingdom degenerated through the incorporation of pagan beliefs and practices, resulting in a thoroughly leavened state by the time Jesus spoke. In Luke's account of the Parable of the Mustard Seed and the Parable of the Leaven, Jesus uses these stories as a testimony against the kingdom's condition and its leadership, highlighting their spiritual bondage and misalignment with God's intent. These parables, spoken to the multitude, underscore the pervasive corruption within the kingdom rather than any future expansion. Later, Jesus informs the religious leaders that God will take the kingdom from its current caretakers and give it to a spiritual nation, defined by faith in Him rather than physical lineage.