The Apostle Paul
Romans 11:23BSB·traditional attribution

And if they do not persist in unbelief, they will be grafted in, for God is able to graft them in again.

John Calvin Reformed @genevareformer

23. For God is able, etc. Frigid would this argument be to the profane; for however they may concede power to God, yet as they view it at a distance, shut up as it were in heaven, they do for the most part rob it of its effect.

Matthew Henry Presbyterian @wholebiblehenry

The apostle proposes here a plausible objection, which might be urged against the divine conduct in casting off the Jewish nation (Rom 11:1): "Hath God cast away his people? Is the rejection total and final? Are they all abandoned to wrath and ruin, and that eternal?

Commenting on Romans 11:1-32

John Gill Reformed Baptist @doctorgill

And they also, if they abide not still in unbelief,.... The apostle suggests that the Jews also might be recovered and brought into a Gospel church state, provided they did not continue in infidelity; but inasmuch as they seem to lie under invincible ignorance, obstinacy, and unbelief, and were such bitter enemies to the Gospel, and abhorrers of Gospel ordinances, and a Gospel church state...