HARDNESS OF HEART — sklēros ('hard, dry, stiff') + kardia. Not a classical Greek word: it was built for the Greek Old Testament to carry a Hebrew idiom, the uncircumcised or stubborn heart (Deuteronomy 10:16, Jeremiah 4:4). ⚠ It does one specific job in Matthew 19:8, and it is a job about LAW: Moses did not COMMAND the certificate of divorce, as the Pharisees claim — he PERMITTED it, and 'for your sklērokardia.' So a provision of the Torah is described as a concession to a condition, given because the ideal could not be enforced on people as they are. That distinction — between what is commanded and what is permitted, and between the beginning and the concession — is the whole of Jesus' answer, and the two Greek verbs (eneteilato / epetrepsen) are kept distinct in this translation for that reason. → first discussed at Matt 19:8