G4645–σκληρύνω–sklērunō

But some grew obstinate in unbelief and spoke evil of the new faith before all the congregation. So Paul left them, and, taking with him those who were disciples, held discussions daily in Tyrannus's lecture-hall.

ἐσκληρύνοντο esklērunonto “were hardened”

This is a proof that wherever He chooses He shows mercy, and wherever he chooses He hardens the heart.

σκληρύνει. sklērunei “He hardens.”

do not harden your hearts as your forefathers did in the time of the provocation on the day of the temptation in the Desert,

σκληρύνητε sklērunēte “shall harden”

On the contrary encourage one another, day after day, so long as To-day lasts, so that not one of you may be hardened through the deceitful character of sin.

σκληρυνθῇ sklērunthēa “may be hardened”

seeing that the warning still comes to us, "To-day, if you hear His voice, do not harden your hearts as your forefathers did in the time of the provocation."

σκληρύνητε sklērunēte “shall harden”

He again definitely mentions a certain day, "To-day," saying long afterwards, by David's lips, in the words already quoted, "To-day, if you hear His voice, do not harden your hearts."

σκληρύνητε sklērunēte “shall harden”