Today, if you will hear His voice, do not harden your hearts as in the rebellion. Beware brethren, lest there be in any of you an evil heart of unbelief in departing from the living God; but exhort one another daily… lest any of you be hardened through the deceitfulness of sin.
Hebrews 3:7, 12-13
F.B. Meyer is one from a previous generation who I can say with confidence–any writing you can find from him will be of great godly wisdom and insight for you.
From his thoughts on the above verses: “Guard against an evil heart–If the heart were in a right condition, faith will be as natural to it as flowers in the spring. As soon as the heart gets into an evil state–harboring sin; cherishing things which you would not excuse in others, permitting unholy thoughts to remain unchecked; then beware! Such a heart is no longer able to believe in God. Its head turns dizzy; its eyes are blinded; and it is in imminent peril of falling irretrievably.
Take heed then; watch and pray; examine yourselves whether you be in the faith! Expose yourself to the searching light of the Spirit. Cultivate the good and honest heart. More skepticism may be traced to neglected prayer than to arguments or the secularist. First men depart from God; then they deny Him.
“Keep your heart with all diligence, for out of it spring the issues of life” Proverbs 4:23.
Guard especially against heart hardening–– Hard hearts are unbelieving ones; therefore, beware of ossification of the heart. The hardest hearts were once soft, and the softest may get hard. Hearts harden gradually, like the freezing of a pond on a frosty night. At first the process can be detected by none but the practiced eye. Then there is a thin film of ice, so slender a needle would fall through. At length it will sustain a pebble, and, if winter hold its broken sway, a child, a man, a crowd, a cart will follow. We get hard through steps of an unperceived process––the constant hearing of truth without obeying it. The knowing of a better and doing the worse. The cherishing of unholy things that seem fair as angels. The refusal to confess the wrong and to profess the right… all these things harden. Beware of the deceitfulness of sin! Take heed to yourselves! Exhort one another daily.
We should see not only to our own heart, but to the heart of our brethren; and exhort one another daily, watching over each other, and seeking to revive drooping piety and re-animate fainting hope. Let us take heed to these things today. Now is God’s time. The Holy Spirit says ‘Today.’ Every day of delay is dangerous, because the hardening process becomes more habitual. Today restore what you have taken wrongfully; adjust a wrong, promote a right. Today renounce some evil habit, some unhallowed pastime, some unlawful friendship. Today leave the wilderness forever, and enter by faith the Land of Promise.