But when some became stubborn (esklērynonto | ἐσκληρύνοντο | imperf pass ind 3 pl) and refused to believe, speaking evil of the Way before the congregation, he withdrew from them, taking the disciples with him, and continued daily to discourse in the lecture hall of Tyrannus.

“You stiff-necked (sklērotrachēloi | σκληροτράχηλοι | voc pl masc) people, uncircumcised in heart and ears! You are always resisting the Holy Spirit. As your fathers were, so also are you.

But because of your stubbornness (sklērotēta | σκληρότητα | acc sg fem) and your unrepentant heart, you are storing up wrath for yourself on the day of wrath, when God’s righteous judgment will be revealed,

to execute judgment on all and to convict all the ungodly of all their ungodly acts that they have committed in their ungodliness, and of all the harsh things (sklērōn | σκληρῶν | gen pl neut) that ungodly sinners have spoken against him.”

Or consider ships: though they are so large and are driven by strong (sklērōn | σκληρῶν | gen pl masc) winds, they are steered by a very small rudder, wherever the impulse of the pilot directs.

And when we had all fallen to the ground, I heard a voice saying to me in the Hebrew language, ‘Saul, Saul, why are you persecuting me? It is hard (sklēron | σκληρόν | nom sg neut) for you to kick against the goads.’

Therefore, when a number of his disciples heard it, they said, “This teaching is difficult (sklēros | σκληρός | nom sg masc); who can understand it?”

Then the one who had received the one talent also came, saying, ‘Master, I knew that you were an unscrupulous (sklēros | σκληρός | nom sg masc) man, reaping where you have not sown and gathering where you scattered no seed;

Later he appeared to the eleven themselves as they were reclining at table; and he reproached their unbelief and hardness (sklērokardian | σκληροκαρδίαν | acc sg fem) of heart, because they had refused to believe those who had seen him resurrected.

But Jesus said to them, “Because of your hardness (sklērokardian | σκληροκαρδίαν | acc sg fem) of heart he wrote this commandment for you.