From Matthew Henry’s Commentary on the whole Bible

http://www.biblestudytools.com/commentaries/matthew-henry-complete/psalms/139.html

Psalm 139 Verses 17-24 Here the psalmist makes application of the doctrine of God’s omniscience, divers ways.

I. He acknowledges, with wonder and thankfulness, the care God had taken of him all his days, v. 17, v. 18. God, who knew him, thought of him, and his thoughts towards him were thoughts of love, thought of good, and not of evil, Jer. 29:11 . God’s omniscience, which might justly have watched over us to do us hurt, has been employed for us, and has watched over us to do us good, Jer. 31:28 . God’s counsels concerning us and our welfare have been,

1. Precious to admiration: How precious are they! They are deep in themselves, such as cannot possibly be fathomed and comprehended. Providence has had a vast reach in its dispensations concerning us, and has brought things about for our good quite beyond our contrivance and foresight. They are dear to us; we must think of them with a great deal of reverence, and yet with pleasure and thankfulness. Our thoughts concerning God must be delightful to us, above any other thoughts.

2. Numerous to admiration: How great is the sum of them! We cannot conceive how many God’s kind counsels have been concerning us, how many good turns he has done us, and what variety of mercies we have received from him. If we would count them, the heads of them, much more the particulars of them, they are more in number than the sand, and yet every one great and very considerable, Ps. 40:5 . We cannot conceive the multitude of God’s compassions, which are all new every morning.

3. Constant at all times: “When I awake, every morning, I am still with thee,under thy eye and care, safe and easy under thy protection.’’ This bespeaks also the continual devout sense David had of the eye of God upon him: When I awake I am with thee, in my thoughts; and it would help to keep us in the fear of the Lord all the day long if, when we awake in the morning, our first thoughts were of him and we did then set him before us

II. He concludes from this doctrine that ruin will certainly be the end of sinners. God knows all the wickedness of the wicked, and therefore he will reckon for it: “Surely thou wilt slay the wicked, O God! for all their wickedness is open before thee, however it may be artfully disguised and coloured over, to hide it from the eye of the world. However thou suffer them to prosper for a while, surely thou wilt slaythem at last.’’ Now observe,

1. The reason why God will punish them, because they daringly affront him and set him at defiance (v. 20): They speak against thee wickedly; they set their mouth against the heavens (Ps. 73:9 ), and shall be called to account for the hard speeches they havespoken against him, Jude. 15, . They are his enemies, and declare their enmity by taking his name in vain, as we show our contempt of a man if we make a by-word of his name, and never mention him but in a way of jest and banter. Those that profane the sacred forms of swearing or praying by using them in an impertinent irreverent manner take God’s name in vain, and thereby show themselves enemies to him. Some make it to be a description of hypocrites: “They speak of thee for mischief; they talk of God, pretending to piety, but it is with some ill design, for a cloak of maliciousness; and, being enemies to God, while they pretend friendship, they take his name in vain; they swear falsely.’’

2. The use David makes of this prospect which he has of the ruin of the wicked.

(1.) He defies them: “Depart from me, you bloody men; you shall not debauch me, for I will not admit your friendship nor have fellowship with you; and you cannot destroy me, for, being under God’s protection, he shall force you to depart from me.’’

(2.) He detests them (v. 21, v. 22): “Lord, thou knowest the heart, and canst witness for me; do not I hate those that hate thee, and for that reason, because they hate thee? I hate them because I love thee, and hate to see such affronts and indignities put upon thy blessed name. Am not I grieved with those that rise up against thee, grieved to see their rebellion and to foresee their ruin, which it will certainly end in?’’ Note, Sin is hated, and sinners are lamented, by all that fear God. “I hate them’’ (that is, “I hate the work of them that turn aside,’’ as he explains himself, Ps. 101:3 ) “with a sincere and perfect hatred; I count those that are enemies to God as enemies to me, and will not have any intimacy with them,’’Ps. 69:8 .

III. He appeals to God concerning his sincerity, v. 23, v. 24. He desires that as far as he was in the wrong God would discover it to him. Those that are upright can take comfort in God’s omniscience as a witness of their uprightness, and can with a humble confidence beg of him to search and try them, to discover them to themselves (for a good man desires to know the worst of himself) and to discover them to others. He that means honestly could wish he had a window in his breast that any man may look into his heart: “Lord, I hope I am not in a wicked way, but see if there be any wicked way in me, any corrupt inclination remaining; let me see it; and root it out of me, for I do not allow it.’’ 2. He desires that, as far as he was in the right, he might be forwarded in it, which he that knows the heart knows how to do effectually: Lead me in the way everlasting.

Note,

(1.) The way of godliness is an everlasting way; it is everlastingly true and good, pleasing to God and profitable to us, and will end in everlasting life. It is the way of antiquity (so some), the good old way.

(2.) All the saints desire to be kept and led in this way, that they may not miss it, turn out of it, nor tire in it.

Response:

Keep me true, Lord Jesus

Lord, only You can keep me true

From enemies  whose vengeance belongs to You,

For guidance that I do not fall into temptations sore

Keep me true to the path You have chosen for me.

Amen.