Matthew 23:21 in the King James Version (KJV) of the Bible reads, "And whoso shall swear by the temple, sweareth by it, and by him that dwelleth therein."

In this verse, Jesus is addressing the Pharisees and scribes, who were the religious leaders of the day. He is speaking to them about their hypocrisy and their misuse of religious oaths and vows. Jesus is revealing the heart condition of these leaders and their tendency to focus on outward appearance rather than on matters of the heart.

The context of this verse is important in understanding its full meaning. In the previous verses, Jesus rebukes the scribes and Pharisees for their hypocritical behavior, for placing heavy burdens on others that they themselves are not willing to bear, and for neglecting the weightier matters of the law such as justice, mercy, and faith. Jesus is pointing out that the religious leaders are focused on making grand oaths and vows, but their hearts are far from God.

The theme of this verse is the importance of integrity and sincerity in our words and actions. Jesus is reminding the religious leaders that it is not enough to simply make oaths and vows by the temple or by anything else. What truly matters is the condition of the heart and the sincerity behind the words spoken. Jesus is challenging the religious leaders to examine their motives and to look beyond the outward appearance of piety to the true condition of their hearts.

The symbolism in this verse lies in the temple itself. The temple was a central and sacred place of worship for the Jewish people. It was a symbol of God's presence among His people and a focal point for their religious practices. By referencing the temple in this verse, Jesus is highlighting the sacredness and importance of religious oaths and vows, and the seriousness with which they should be taken. The temple represents the holiness and presence of God, and by swearing by it, one is invoking the name of God Himself. This is a serious matter and one that Jesus is not taking lightly in His rebuke of the religious leaders.

Ultimately, this verse serves as a reminder to all believers of the importance of sincerity and integrity in our words and actions. It is a call to examine our motives and the condition of our hearts, and to not be swayed by outward appearances of religiosity. Our words should be a reflection of the sincerity of our hearts, and our actions should align with the values and principles of God's kingdom.

In conclusion, Matthew 23:21 in the King James Version of the Bible challenges us to consider the condition of our hearts and the sincerity of our words and actions. It serves as a reminder of the importance of integrity and the seriousness of making oaths and vows, especially when invoking the name of God. This verse calls us to live with sincerity and authenticity, and to focus on the matters of the heart rather than on outward appearances.