Psalm 61:6 explicitly prays for the king's life to endure — the same petition that is answered in Psalm 21:4 with 'length of days forever'.

Psalm 91:16 promises long life and salvation to the faithful, directly mirroring the king's granted 'length of days forever'.

Psalm 72:15 prays for the king to live long, directly matching the granted request for 'length of days forever' here.

Psalm 16:10 promises that God's holy one will not see corruption — a deeper hope of resurrection underlying the 'length of days forever' given to the king.

Psalm 16:11 describes the path of life and eternal pleasures in God's presence — the same blessed outcome as the 'length of days forever' granted to the king.

Psalm 89:29 promises an eternal throne and offspring — a covenant blessing that complements the personal 'length of days forever' granted to the king.

Psalm 89:36 extends the promise of eternal duration to David's offspring and throne, paralleling the king's personal eternal life here.

Psalm 89:37 continues the same theme: David's throne established forever like the moon, echoing the eternal life granted to the king.

Psalm 37:18 says the blameless have an eternal inheritance, echoing the king's 'length of days forever' as a reward.

Psalm 72:17 prays for the king's name to endure forever — a parallel blessing of eternal significance to the 'length of days forever' given here.

1 Kings 3:14 conditions long life on obedience, while here the king receives it unconditionally as a gift.

Proverbs 3:2 promises length of days to those who keep wisdom — a similar blessing of long life, though here it's granted directly by God to the king.

Proverbs 3:16 also attributes length of days to wisdom — a parallel blessing, though here the king receives it as a direct gift from God.

Proverbs 10:27 says fearing the Lord prolongs days — a parallel concept of extended life, though here the king's life is granted by God's favor.