The Scofield Bible Commentary, by Cyrus Ingerson Scofield, [1917], at sacred-texts.com
Have
This Psalm must ever be, in its successive steps, the mould of the experience of a sinning saint who comes back to full communion and service. The steps are:
(1) sin thoroughly judged before God (vs. 1-6);
(2) forgiveness and cleansing through the blood (v. 7.f.c.)
(3) cleansing (v. 7,1,c, to 10.) Compare (Joh 13:4-10); (Eph 5:26); (Jo1 1:9).
(4) Spirit-filled for joy and power (vs. 11,12);
(5) service (v. 13);
(6) worship (vs 14-17);
(7) the restored saint in fellowship with God, not about self, but about the blessing of Zion. Personally, it was David's pathway to restored communion after his sin with Bathsheba. Dispensationally, it will be the pathway of returning Israel. (Deu 30:1-10).
Hyssop
Hyssop was the little shrub (Kg1 4:33) with which the blood and water of purification were applied. (Lev 14:1-7); (Num 19:1-19). Cleansing in Scripture is twofold:
(1) Of a sinner from the guilt of sin; the blood ("hyssop") aspect;
(2) of a saint from the defilement of sin -- the water ("wash me") aspect;
(3) Under grace the sinner is purged by blood when he believes (Mat 26:28); (Heb 1:3); (Heb 9:12); (Heb 10:14). Both aspects of cleansing, by blood and by water, are brought out in; (Joh 13:10); (Eph 5:25); (Eph 5:26).
"He that is bathed needeth not save to wash his feet"; "Christ loved the church and gave Himself for it redemption by "blood, "hyssop," the "bath"] that He might sanctify and cleanse "it with the washing by the word": answering to the "wash me" of verse 7 (Psa 51:7).
Take not
No believer of this dispensation, aware of the promise of His abiding (Joh 14:16) should pray, "Take not Thy Holy Spirit from me." (Eph 4:30) but while Christian position is not found here, Christian experience in essence is.