"“Blessed is he whose transgression is forgiven, whose sin is covered. Blessed is the man unto whom the Lord imputeth not iniquity, And in whose spirit there is no guile.” Psalm 32:1, 2 . SC 25.1"
"Blessed is he whose transgression is forgiven, whose sin is covered."
EGW directly quotes Psalm 32:1, making this a clear and undeniable explicit allusion.
"“Have mercy upon me, O God, according to Thy loving-kindness: According unto the multitude of Thy tender mercies blot out my transgressions.... For I acknowledge my transgressions: and my sin is ever before me.... Purge me with hyssop, and I shall be clean: wash me, and I shall be whiter than snow.... Create in me a clean heart, O God; And renew a right spirit within me. Cast me not away from Thy presence; And take not Thy Holy Spirit from me. Restore unto me the joy of Thy salvation; And uphold me with Thy free spirit.... Deliver me from bloodguiltiness, O God, Thou God of my salvation: And my tongue shall sing aloud of Thy righteousness.” Psalm 51:1-14 . SC 25.2"
"Have mercy upon me, O God, according to thy lovingkindness: according unto the multitude of thy tender mercies blot out my transgressions. Wash me throughly from mine iniquity, and cleanse me from my sin. For I acknowledge my transgressions: and my sin is ever before me. Against thee, thee only, have I sinned, and done this evil in thy sight: that thou mightest be justified when thou speakest, and be clear when thou judgest. Behold, I was shapen in iniquity; and in sin did my mother conceive me. Behold, thou desirest truth in the inward parts: and in the hidden part thou shalt make me to know wisdom. Purge me with hyssop, and I shall be clean: wash me, and I shall be whiter than snow. Make me to hear joy and gladness; that the bones which thou hast broken may rejoice. Hide thy face from my sins, and blot out all mine iniquities. Create in me a clean heart, O God; and renew a right spirit within me. Cast me not away from thy presence; and take not thy holy spirit from me. Restore unto me the joy of thy salvation; and uphold me with thy free spirit. Then will I teach transgressors thy ways; and sinners shall be converted unto thee. Deliver me from bloodguiltiness, O God, thou God of my salvation: and my tongue shall sing aloud of thy righteousness."
Ellen White directly references Psalms 51:1-14 in this passage.
"A repentance such as this, is beyond the reach of our own power to accomplish; it is obtained only from Christ, who ascended up on high and has given gifts unto men. SC 25.3"
"Wherefore he saith, When he ascended up on high, he led captivity captive, and gave gifts unto men."
EGW directly quotes and interprets Ephesians 4:8 in the context of receiving gifts (repentance) from Christ.
"Him hath God exalted with his right hand to be a Prince and a Saviour, for to give repentance to Israel, and forgiveness of sins."
Both passages connect Christ with the giving of repentance. While EGW doesn't directly quote Acts 5:31, the theme is very similar.