Romans 9:17 For the scripture saith unto Pharaoh, Even for this same purpose have I raised thee up, that I might shew my power in thee, and that my name might be declared throughout all the earth.
Pharaoh exemplifies those God hardens as defined in Romans 9:18. The “division” of Luke 12:51 is exemplified by human beings God makes merciful pursuant to God’s will being divided from human beings God hardens to remove them from God’s process pursuant to God’s will.
Romans 9:18 Therefore hath he mercy on whom he will have mercy, and whom he will he hardeneth.
English “hath he mercy” emboldened in Romans 9:18 was mistranslated from Greek verb 1653 eleeo subjectively meaning to make merciful. Grammatical objects of God will be made merciful during this earth age. God’s “seven thousand” “election” will superimpose God’s mercy by performing the action of Greek verb 1653 eleeo during the “thousand years” “Lord’s day” which will occur between this earth age and the eternal age that follows. The “thousand years” “Lord’s day” in which “God our Saviour” “will have all men to be saved, and to come unto the knowledge of the truth”.
English “he hardeneth” emboldened in Romans 9:18 was translated from Greek verb 4645 skleruno. Grammatical subjects perform a verb’s action. Grammatical objects receive the action performed. In that context Greek verb 4645 skleruno subjectively means to harden and objectively means to be hardened. Greek verb 4645 skleruno was translated into “harden” in Hebrews 4:7. If you want to know God’s definition of Greek verb 4645 skleruno you should study all the words in every verse containing Greek words 4641-4645.