The verse Psalms 89:21 in the King James Version of the Bible reads, "With whom my hand shall be established: mine arm also shall strengthen him." This verse is part of a larger passage in Psalm 89 which is a prayer of praise and a meditation on the faithfulness of God. The psalmist reflects on God's covenant with David and expresses confidence in God's ability to fulfill his promises.

The context of this verse is important for understanding its meaning. In the preceding verses, the psalmist is praising God for his greatness, faithfulness, and sovereignty. The psalmist declares that God is to be greatly feared and revered above all gods, and that he is a covenant-keeping God. The psalmist also reflects on God's promise to establish David's throne forever and to make his descendants endure forever.

In verse 21, the psalmist speaks of God's commitment to David and his descendants. The phrase "With whom my hand shall be established" conveys the idea that God will firmly establish and support the chosen one, in this case, David. This is a declaration of God's commitment and support for David's reign and dynasty. The imagery of God's hand being established also suggests his ongoing presence and involvement in the affairs of the Davidic line.

The verse continues with the promise, "mine arm also shall strengthen him." This speaks to God's power and might, which will be present to strengthen and uphold David. The symbolism of God's arm conveys the idea of strength and support, representing God's ability to protect and defend his chosen one.

The themes present in this verse include God's faithfulness, sovereignty, and power. The psalmist is expressing confidence in God's ability to fulfill his promises and uphold the Davidic dynasty. The imagery of God's hand and arm conveys the idea of support and strength, affirming God's commitment to his chosen people.

In a broader context, this verse can also be seen as a reflection of God's faithfulness to his people throughout history. God's hand and arm are symbols of his presence and power, and his commitment to establishing and strengthening those whom he has chosen.

The verse can also be seen as a foreshadowing of the coming of Jesus Christ, who is understood in Christian theology as the ultimate fulfillment of God's promise to establish the line of David forever. In this sense, the verse can be interpreted as a prophecy of the coming Messiah, in whom God's hand and arm are established for the salvation and strength of all who believe in him.

In conclusion, Psalms 89:21 is a powerful declaration of God's faithfulness, sovereignty, and power. The imagery of God's hand and arm conveys the idea of support and strength, affirming God's commitment to his chosen people and foreshadowing the coming of the Messiah. This verse serves as a reminder of God's ongoing presence and involvement in the lives of his people, and as an encouragement to trust in his promises and rely on his strength.