Adam Clarke on Genesis 17:14

The uncircumcised - shall be cut off from his people - By being cut off some have imagined that a sudden temporal death was implied; but the simple meaning seems to be that such should have no right to nor share in the blessings of the covenant, which we have already seen were both of a temporal and spiritual kind; and if so, then eternal death was implied, for it was impossible for a person who had not received the spiritual purification to enter into eternal glory. The spirit of this law extends to all ages, dispensations, and people; he whose heart is not purified from sin cannot enter into the kingdom of God. Reader, on what is thy hope of heaven founded?