https://www.studylight.org/dictionaries/hbd/c/conscience.html
Bible Dictionaries Holman Bible Dictionary
Conscience refers in general to that human moral awareness that judges
an action right or wrong.
Although the word “conscience” does [not] appear in the Old Testament,
the Hebrew word usually translated “heart” does refer to conscience in
a number of passages, for example, “Afterward David's heart smote him”
(1 Samuel 24:5 ). Compare 2 Samuel 24:10 ; Job 27:6.
2Sam. 24:10 (KJV) - And David's heart smote him after that he had
numbered the people. And David said unto the LORD, I have sinned
greatly in that I have done: and now, I beseech thee, O LORD, take
away the iniquity of thy servant; for I have done very foolishly.
Job 27:6 (KJV) - My righteousness I hold fast, and will not let it go: my heart shall not reproach me so long as I live.
The New Testament also uses this Hebraic reference to conscience: “if
our heart condemn us” (1 John 3:20-21 .) The word for “reins” or
“kidneys” sometimes refers to conscience. In Psalm 16:7 the psalmist
thanked God for giving him counsel and because his reins or kidneys
admonished him, meaning his conscience reproved him. (See Psalm 73:21
for “heart” and “reins” in the same verse.)
Psa. 73:21 (KJV) - Thus my heart was grieved, and I was pricked in my reins.
“Conscience” in the New Testament is the translation of a Greek word
derived from a verb that means “to know with.” This suggests a moral
consciousness which compares an action with a standard. Paul, it
seems, took a word from popular Greek usage in Corinth and used it to
reply to some of the Corinthian Christians.
For Paul, God is the Creator and Sustainer of all things. God judges
persons by His standards as revealed in Jesus Christ. These standards
are reflected in His creation and especially in persons who are
morally responsible because of their capacity of choice.
To Paul the “conscience” is a person's painful reaction to a past act
which does not meet the standard. A person can react wrongly because
of wrong information, wrong environment, and wrong habit. Yet Paul
would have said that, in spite of these liabilities, a person's
conscience must be obeyed. Paul, however, would not have said that a
person has no other guide. If past actions have not been such as to
produce painful reactions, the person is said to have a “pure
conscience” (1 Timothy 3:9 ; 2 Timothy 1:3 ). When sensitive and
active in judging past acts, the conscience is said to be “good” (Acts
23:1 ; 1Timothy 1:5,1 Timothy 1:19 ; 1Peter 3:16,1 Peter 3:21 ;
Hebrews 13:18 ) or “void of offence toward God” (Acts 24:16 ). If the
conscience is not active in judging past acts, it is said to be “weak”
(1Corinthians 8:7,1Corinthians 8:10,1 Corinthians 8:12 ) and may be
wounded (1 Corinthians 8:12 ). When the conscience is insensitive, it
is “seared” (1 Timothy 4:2 ). The sinful conscience is “defiled”
(Titus 1:15 ) or “evil” (Hebrews 10:22 ).
In 1 Corinthians 4:4 , Paul used the verb from which the word for
“conscience” is derived. He wrote: “For I know nothing by myself.”
This phrase means “my conscience does not accuse me.” Paul completed
the sentence by saying: “yet am I not hereby justified: but he that
judgeth me is the Lord.” Paul, in short, taught that a pure conscience
is valuable, but that Christ is the final standard by which a person
is judged.