Psalm 139:12 The omniscience of God..

O Lord , thou hast searched me, and known me.

Thou knowest my downsitting and mine uprising, thou understandest my thought afar off.

Thou compassest my path and my lying down, and art acquainted with all my ways.

For there is not a word in my tongue, but, lo, O Lord , thou knowest it altogether.

Thou hast beset me behind and before, and laid thine hand upon me.

Such knowledge is too wonderful for me; it is high, I cannot attain unto it.

Whither shall I go from thy spirit? or whither shall I flee from thy presence?

If I ascend up into heaven, thou art there: if I make my bed in hell, behold, thou art there.

If I take the wings of the morning, and dwell in the uttermost parts of the sea;

Even there shall thy hand lead me, and thy right hand shall hold me.

If I say, Surely the darkness shall cover me; even the night shall be light about me.

Yea, the darkness hideth not from thee; but the night shineth as the day: the darkness and the light are both alike to thee.

For thou hast possessed my reins: thou hast covered me in my mother's womb.

I will praise thee; for I am fearfully and wonderfully made: marvellous are thy works; and that my soul knoweth right well.

My substance was not hid from thee, when I was made in secret, and curiously wrought in the lowest parts of the earth.

Thine eyes did see my substance, yet being unperfect; and in thy book all my members were written, which in continuance were fashioned, when as yet there was none of them.

How precious also are thy thoughts unto me, O God! how great is the sum of them!

If I should count them, they are more in number than the sand: when I awake, I am still with thee.

Surely thou wilt slay the wicked, O God: depart from me therefore, ye bloody men.

For they speak against thee wickedly, and thine enemies take thy name in vain.

Do not I hate them, O Lord , that hate thee? and am not I grieved with those that rise up against thee?

I hate them with perfect hatred: I count them mine enemies.

Search me, O God, and know my heart: try me, and know my thoughts:

And see if there be any wicked way in me, and lead me in the way everlasting.
Psalms 139:1‭-‬24

Tozer in his book Knowledge of the Holy Addresses the OMNISCIENCE of God

"The Divine Omniscience"
Lord, Thou knowest all things; Thou knowest my downsitting and mine uprising and art
acquainted with all my ways. I can inform Thee of nothing and it is vain to try to hide
anything from Thee. In the light of Thy perfect knowledge I would be as artless as a
little child. Help me to put away all care, for Thou knowest the way that I take and when
Thou hast tried me I shall come forth as gold. Amen.
To say that God is omniscient is to say that He possesses perfect knowledge and
therefore has no need to learn. But it is more: it is to say that God has never learned and
cannot learn.
The Scriptures teach that God has never learned from anyone. “Who hath directed the
Spirit of the Lord, or being his counsellor hath taught him? With whom took he counsel,
and who instructed him, and taught him in the path of judgment, and taught him
knowledge, and shewed to Him the way of understanding?”
”For who hath known the mind of the Lord? or who hath been His counsellor?" These
rhetorical questions put by the prophet and the apostle Paul declare that God has never
learned.
From there it is only a step to the conclusion that God cannot learn. Could God at any
time or in any manner receive into His mind knowledge that He did not possess and had
not possessed from eternity, He would be imperfect and less than himself. To think of a
God who must sit at the feet of a teacher, even though that teacher be an archangel or a
seraph, is to think of someone other than the Most High God, maker of heaven and
earth.
This negative approach to the divine omniscience is, I believe, quite justified in the
circumstances. Since our intellectual knowledge of God is so small and obscure, we can
sometimes gain considerable advantage in our struggle to understand what God is like
by the simple expedient of thinking what He is not like. So far in this examination of the
attributes of God we have been driven to the free use of negatives. We have seen that
God had no origin, that He had no beginning, that He requires no helpers, that He
suffers no change, and that in His essential being there are no limitations.
This method of trying to make men see what God is like by showing them what He is
not like is used also by the inspired writers in the Holy Scriptures. “Hast thou not
known? hast thou not heard,” cries Isaiah, “that the everlasting God, the Lord, the
Creator of the ends of the earth, fainteth not, neither is weary?” And that abrupt
statement by God Himself, “I am the Lord, I change not,” tells us more about the divine
omniscience than could be told in a ten-thousand word treatise, were all negatives
arbitrarily ruled out. God’s eternal truthfulness is stated negatively by the apostle Paul,
“God... cannot lie”; and when the angel asserted that “with God nothing shall be
impossible,” the two negatives add up to a ringing positive.
That God is omniscient is not only taught in the Scriptures, it must be inferred also from
all else that is taught concerning Him. God perfectly knows Himself and, being the
source and author of all things, it follows that He knows all that can be known. And this
He knows instantly and with a fullness of perfection that includes every possible item of
knowledge concerning everything that exists or could have existed anywhere in the
universe at any time in the past or that may exist in the centuries or ages yet unborn.

God knows instantly and effortlessly all matter and all matters, all mind and every
mind, all spirit and all spirits, all being and every being, all creaturehood and all
creatures, every plurality and all pluralities, all law and every law, all relations, all
causes, all thoughts, all mysteries, all enigmas, all feeling, all desires, every unuttered
secret, all thrones and dominions, all personalities, all things visible and invisible in
heaven and in earth, motion, space, time, life, death, good, evil, heaven, and hell.
Because God knows all things perfectly, He knows no thing better than any other thing,
but all things equally well. He never discovers anything. He is never surprised, never
amazed. He never wonders about anything nor (except when drawing men out for their
own good) does He seek information or ask questions.
God is self-existent and self-contained and knows what no creature can ever know -
Himself, perfectly.
”The things of God knoweth no man, but the Spirit of God.” Only the Infinite can know
the infinite.
In the divine omniscience we see set forth against each other the terror and fascination
of the Godhead. That God knows each person through and through can be a cause of
shaking fear to the man that has something to hide - some unforsaken sin, some secret
crime committed against man or God. The unblessed soul may well tremble that God
knows the flimsiness of every pretext and never accepts the poor excuses given for
sinful conduct, since He knows perfectly the real reason for it. “Thou hast set our
iniquities before thee, our secret sins in the light of thy countenance.” How frightful a
thing to see the sons of Adam seeking to hide among the trees of another garden. But
where shall they hide? “Whither shall I go from thy spirit? or whither shall I flee from
thy presence?... If I say, Surely the darkness shall cover me; even the night shall be light
about me. Yea, the darkness hideth not from thee; but the night shineth as the day.”
And to us who have fled for refuge to lay hold upon the hope that is set before us in the
gospel, how unutterably sweet is the knowledge that our Heavenly Father knows us
completely. No talebearer can inform on us, no enemy can make an accusation stick; no
forgotten skeleton can come tumbling out of some hidden closet to abash us and expose
our past; no unsuspected weakness in our characters can come to light to turn God away
from us, since He knew us utterly before we knew Him and called us to Himself in the
full knowledge of everything that was against us. “For the mountains shall depart, and
the hills be removed; but my kindness shall not depart from thee, neither shall the
covenant of my peace be removed, saith the Lord that hath mercy on thee.”
Our Father in heaven knows our frame and remembers that we are dust. He knew our
inborn treachery, and for His own sake engaged to save us (Isa. 48:8-11). His only
begotten Son, when He walked among us, felt our pains in their naked intensity of
anguish. His knowledge of our afflictions and adversities is more than theoretic; it is
personal, warm, and compassionate. Whatever may befall us, God knows and cares as
no one else can.
He doth give His joy to all; He becomes an infant small; He becomes a
man of woe; He doth feel the sorrow too.
Think not thou canst sigh a sigh
And thy Maker is not by;
Think not thou canst weep a tear
And thy Maker is not near.
O! He gives to us His joy