James Montgomery Boice write in his commentary on Psalm 139:
“Sometimes we speak of ‘doing theology’ today, and we often talk about the conflict between the head and the heart, saying that either one alone is inadequate. A theology that is all of the head is cold, dry, barren, and of little practical value. A theology that is all heart may be warm, comforting, and practical, but it will lack substance, and because it does it will be subject to every theological fad that comes along and will not hold up in hard times.”
Boice goes on to say that Psalm 139 is both head and heart, telling us of God’s nature, but in a very personal way. The Psalmist shows us how God is omniscient, omnipresent and omnipotent in our own lives. No matter what we think, or where we go, He is there and He already knows. He knows more about us than we know about Him, or ourselves. He is not distant to us, but involved in the life of the believer and all this is very comforting to those of us who struggle with the trials of life. He is a loving God who cares deeply about us and we can trust in Him.
For the Chief Musician. A Psalm of David.
139 O Lord, You have searched me and known me.
2 You know my sitting down and my rising up;
You understand my thought afar off.
3 You comprehend my path and my lying down,
And are acquainted with all my ways.
4 For there is not a word on my tongue,
But behold, O Lord, You know it altogether.
5 You have hedged me behind and before,
And laid Your hand upon me.
6 Such knowledge is too wonderful for me;
It is high, I cannot attain it.
7 Where can I go from Your Spirit?
Or where can I flee from Your presence?
8 If I ascend into heaven, You are there;
If I make my bed in hell, behold, You are there.
9 If I take the wings of the morning,
And dwell in the uttermost parts of the sea,
10 Even there Your hand shall lead me,
And Your right hand shall hold me.
11 If I say, “Surely the darkness shall fall[a] on me,”
Even the night shall be light about me;
12 Indeed, the darkness shall not hide from You,
But the night shines as the day;
The darkness and the light are both alike to You.
13 For You formed my inward parts;
You covered me in my mother’s womb.
14 I will praise You, for I am fearfully and wonderfully made;[b]
Marvelous are Your works,
And that my soul knows very well.
15 My frame was not hidden from You,
When I was made in secret,
And skillfully wrought in the lowest parts of the earth.
16 Your eyes saw my substance, being yet unformed.
And in Your book they all were written,
The days fashioned for me,
When as yet there were none of them.
17 How precious also are Your thoughts to me, O God!
How great is the sum of them!
18 If I should count them, they would be more in number than the sand;
When I awake, I am still with You.
19 Oh, that You would slay the wicked, O God!
Depart from me, therefore, you bloodthirsty men.
20 For they speak against You wickedly;
Your enemies take Your name in vain.[c]
21 Do I not hate them, O Lord, who hate You?
And do I not loathe those who rise up against You?
22 I hate them with perfect hatred;
I count them my enemies.
23 Search me, O God, and know my heart;
Try me, and know my anxieties;
24 And see if there is any wicked way in me,
And lead me in the way everlasting.