Isaiah 1:18
15 When you spread out your hands in prayer, I look the other way; when you offer your many prayers, I do not listen because your hands are covered with blood. 16 Wash! Cleanse yourselves! Remove your sinful deeds from my sight. Stop sinning. 17 Learn to do what is right. Promote justice. Give the oppressed reason to celebrate. Take up the cause of the orphan. Defend the rights of the widow. 18 “Come, let’s consider your options,” says the Lord. “Though your sins have stained you like the color red, you can become white like snow; though they are as easy to see as the color scarlet, you can become white like wool.
Psalm 51:9
6 Look, you desire integrity in the inner man; you want me to possess wisdom. 7 Cleanse me with hyssop and I will be pure; wash me and I will be whiter than snow. 8 Grant me the ultimate joy of being forgiven. May the bones you crushed rejoice. 9 Hide your face from my sins. Wipe away all my guilt. 10 Create for me a pure heart, O God. Renew a resolute spirit within me.
Notes and References
"... Scholars often note numerous prophetic allusions within Psalm 51. Both lexical and thematic commonalities have led scholars to posit a connection between the psalm and the traditions of Isaiah, Jeremiah, Ezekiel, etc. Some find the allusions so compelling that they go so far as to argue for dependence ... in Psalm 51, the speaker twice petitions God to "wash" him of his sins (51:4, 9). Although washing with water is not an unusual Image in the Hebrew Bible, used often to describe physical cleansing or ritual purification, it Is an unexpected concept here as it is applied to sin. Here In Psalm 51, and In several passages in Isaiah and Jeremiah, washing is specified as a solution to sin; however, in each of these passages the reference to washing is metaphorical ..."
DiFransico, Lesley Identifying Inner-Biblical Allusion through Metaphor: Washing Away Sin in Psalm 51 (pp. 542-557) Vetus Testamentum 65, 2015