Buy the truth - Acquire the knowledge of God at all events; and in order to do this, too much pains, industry, and labor cannot be expended.

And sell it not - When once acquired, let no consideration deprive thee of it. Cleave to and guard it, even at the risk of thy life. Coverdale translates: "Labour for to get the treuth; sell not awaye wissdome."

buy

Proverbs 2:2-4 So that you incline your ear to wisdom, and apply your heart to understanding...

Proverbs 4:5-7 Get wisdom, get understanding: forget it not; neither decline from the words of my mouth...

Proverbs 10:1 The proverbs of Solomon. A wise son makes a glad father: but a foolish son is the heaviness of his mother.

Proverbs 16:16 How much better is it to get wisdom than gold! and to get understanding rather to be chosen than silver!

Proverbs 17:16 Why is there a price in the hand of a fool to get wisdom, seeing he has no heart to it?

Job 28:12-19 But where shall wisdom be found? and where is the place of understanding...

Psalm 119:72,127 The law of your mouth is better to me than thousands of gold and silver...

Isaiah 55:1 Ho, every one that thirsts, come you to the waters, and he that has no money; come you, buy, and eat...

Matthew 13:44,46 Again, the kingdom of heaven is like to treasure hid in a field; the which when a man has found, he hides...

Philippians 3:7,8 But what things were gain to me, those I counted loss for Christ...

Revelation 3:18 I counsel you to buy of me gold tried in the fire, that you may be rich; and white raiment, that you may be clothed...

sell

Matthew 16:26 For what is a man profited, if he shall gain the whole world, and lose his own soul? or what shall a man give in exchange for his soul?

Acts 20:23 Save that the Holy Ghost witnesses in every city, saying that bonds and afflictions abide me.

Hebrews 11:26 Esteeming the reproach of Christ greater riches than the treasures in Egypt: for he had respect to the recompense of the reward.

Revelation 12:11 And they overcame him by the blood of the Lamb, and by the word of their testimony; and they loved not their lives to the death.

Three Important Precepts
A sermon (No. 2152) intended for reading on Lord's Day, July 13th, 1890, delivered by C. H. Spurgeon at the Metropolitan Tabernacle, Newington, on Lord's Day Evening, June 22nd, 1890. "Hear thou, my son, and be wise, and guide thine heart in the way."--Proverbs 23:19. The words are very direct and personal; and that is what I wish my sermon to be. My soul is more and more set upon immediate conversions. I have no voice with which to play the orator; I have only enough strength to be an earnest pleader …
C.H. Spurgeon—Sermons on Proverbs

The Comforts Belonging to Mourners
Having already presented to your view the dark side of the text, I shall now show you the light side, They shall be comforted'. Where observe: 1 Mourning goes before comfort as the lancing of a wound precedes the cure. The Antinomian talks of comfort, but cries down mourning for sin. He is like a foolish patient who, having a pill prescribed him, licks the sugar but throws away the pill. The libertine is all for joy and comfort. He licks the sugar but throws away the bitter pill of repentance. If …
Thomas Watson—The Beatitudes: An Exposition of Matthew 5:1-12

Of Internal Acts
Of Internal Acts Acts are distinguished into External and Internal. External acts are those which bear relation to some sensible object, and are either morally good or evil, merely according to the nature of the principle from which they proceed. I intend here to speak only of Internal acts, those energies of the soul, by which it turns internally to some objects, and averts from others. If during my application to God I should form a will to change the nature of my act, I thereby withdraw myself …
Madame Guyon—A Short and Easy Method of Prayer