From this website:
“The Hebrew term for ‘conscience’, matzpun, is a relative newcomer in Jewish literature. There is no expression for ‘conscience’ in the Biblical or Rabbinic texts. Matzpun occurs in the medieval philosophical literature, but with a vague meaning. Serious discussions of conscience, together with related concepts like autonomy, natural law, absolute and relative moral values, ethical empowerment and the like, have really come into their own only in the post-Enlightenment period.”
This appears to be true: In the course of research on the concept of “conscience” (Greek συνειδησις), I was somewhat surprised to discover that of the 31 instances of the word in the Bible, none are in the Old Testament. This fact will present some challenges to the project of grounding on the Old Testament any subjective and internal qualifications for participation in the Lord’s Supper. Of course, the fact that the word is not used doesn’t mean the concept is not present or at work. But it does mean that those who believe a personal and internal awareness of one’s sins to be a prerequisite for participation in the Supper will have to do some extra work to explain how the mechanics of the New Testament’s sacraments are not radically different from the mechanics of the Old Testament’s sacraments.