John Calvin on John 8:35

35. Now the slave remaineth not in the house always. He adds a comparison, taken from the laws and from political law, to the effect that a slave, though he may have power for a time, yet is not the heir of the house; from which he infers that there is no perfect and durable freedom, but what is obtained through the Son In this manner he accuses the Jews of vanity, because they hold but a mask instead of the reality; for, as to their being Abraham’s offspring, they were nothing but a mask. They held a place in the Church of God, but such a place as Ishmael, a slave, rising up against his freeborn brother, usurped for a short time, (Galatians 4:29.) The conclusion is, that all who boast of being Abraham’s children have nothing but an empty and deceitful pretense.