Any corruption concealed, any lust harboured, any vicious appetite indulged, any sinful course persisted in. It may refer either to mental errors or evil practices; and may be explained in the following particulars.
1 It does not imply that the Psalmist thought himself entirely free from sin
2 He hoped that sin was not predominant
3 Though sin did not reign yet he was afraid that more sin remained in him than he was aware of
4 What of this nature he was ignorant of, he desires to be taught
Here we may remark the object which David had in view and his desires respecting it.
(1) The way of acceptance with God; and that is Christ, who hath with the greatest solemnity declared, I am the way, the truth, and the life; no man cometh unto the Father but by me (John 14:6)
(2) The way of instituted worship
(3) The way of sound doctrine, in opposition to falsehood and error. ... Now it is a great thing to know the way of truth and to walk in it; to have the judgment well informed in all the essential parts of revealed religion and at the same time feel their quickening and holy influence. This was David's desire, and will be the desire of every real Christian.
(4) The way of holiness and obedience, called in Scripture the way of God's statutes, testimonies, etc. This is a plain way, a pleasant way, a safe way; and the longer we walk in it the more apprised we shall be of its excellence and the advantages arising from it.
Now this way, in whatever light we consider it, may be called the way everlasting because,
(1) It was appointed from everlasting
(2) It is right in its own nature and therefore everlasting; being agreeable to the reason and fitness of things and founded upon the divine perfections.
(3) It is a path which the saints have trod in all ages; the patriarchs and prophets under the Old Testament and the apostles under the new. It was the character of good men of old, and is equally applicable to good men in every age, that they walked with God. ...
(4) It leads to and will end in everlasting life. Say ye to the righteous, it shall be well with him - They that have done good shall come forth to the resurrection of life. There is a great difference between the death of a sinner, and that of a saint; and there will be a greater difference afterwards.
We shall now proceed to notice,
(1) That the Psalmist stood in need of guidance: and what was needful to him is needful to all. The path in which we are called to go is strait and narrow, and sometimes intricate: it lies through an enemy's country, by the lion's den and mountains of leopards. ... Nothing is more dangerous than to lean to our own understanding. Hence it is a saying of Bernard, "He that is his own teacher is sure to have a fool for his master." And a greater than Bernard could say, Oft Lord, I know that the way of man is not in himself; it is not in man that walketh to direct his steps.
(2) That he had a sense of his need.
(3) That he entertained high and exalted thoughts of God, as every way capable of the work which he here assigns to him.
If secret fraud should dwell
Within this heart of mine,
Purge out, O God! that cursed leaven,
And make me wholly thine.
If any rival there,
Dares to usurp the throne,
Oh tear the infernal traitor thence,
And reign thyself alone.
Is any lust concealed?
Bring it to open view;
Search, search, dear Lord, my inmost soul,
And all its powers renew.