Genesis 17:5

For the promise, that he should be the heir of the world, was not to Abraham, or to his seed, through the law, but through the righteousness of faith. For if they which are of the law be heirs, faith is made void, and the promise made of none effect: Because the law worketh wrath: for where no law is, there is no transgression. Therefore it is of faith, that it might be by grace; to the end the promise might be sure to all the seed; not to that only which is of the law, but to that also which is of the faith of Abraham; who is the father of us all, (As it is written, I have made thee a father of many nations,) before him whom he believed, even God, who quickeneth the dead, and calleth those things which be not as though they were. [Genesis 17:5] Who against hope believed in hope, that he might become the father of many nations; according to that which was spoken, So shall thy seed be. And being not weak in faith, he considered not his own body now dead, when he was about an hundred years old, neither yet the deadness of Sara's womb: He staggered not at the promise of God through unbelief; but was strong in faith, giving glory to God; And being fully persuaded that, what he had promised, he was able also to perform. And therefore it was imputed to him for righteousness. Now it was not written for his sake alone, that it was imputed to him; But for us also, to whom it shall be imputed, if we believe on him that raised up Jesus our Lord from the dead; Who was delivered for our offences, and was raised again for our justification.

Many responses are given to Abraham by God, but they are not all delivered to one and the same man. For some are to Abram and some to Abraham; that is, some are expressed after the change of name and others while he was still known by his name given at birth. And first indeed, before the change of name, God delivered to Abraham the oracle that says, “Go out from your country and from your kindred and from your father’s house,” and the rest. But no order is given in this about the covenant of God, no order about circumcision. For it was not possible while he was still Abram and was bearing the name of his physical birth to receive the covenant of God and the mark of circumcision. But when “he went out from his country and his kindred,” then responses of a more sacred kind are delivered to him at this time. First God says to him, “You shall no longer be called Abram, but Abraham shall be your name.” Then at once he received the covenant of God and accepted circumcision as a sign of faith that he could not accept while he was still in his father’s house and in the relationship of flesh and while he was still called Abram.

For a name is changed, with a letter added, so that he would be called Abraham instead of Abram, which means 'father of a multitude', as the Latin interpretation has it, or 'sublime father', 'chosen father'; or so that he would become a father and the father of a son. He was vain when he did not know God; he became chosen after he knew God. He was a father when he had offspring by a slave woman; but he was not the father of a son, because he did not have a son who was conceived in lawful marriage. Sarah gave birth, and he became the father of a son.

Verse 7. "And the overseer of the eunuchs imposed names upon them, calling Daniel Belteshazzar (Balthasar), and Hananiah Shadrach, and Mishael Meshach, and Azariah Abednego." It was not only the overseer or master of the eunuchs (as others have rendered it, the "chief-eunuch") who changed the names of saints, but also Pharaoh called Joseph in Egypt Somtonphanec (Genesis 41:45), for neither of them wished them to have Jewish names in the land of captivity. Wherefore the prophet says in the Psalm: "How shall we sing the Lord's song in a strange land?" (Psalm 137:4). Furthermore the Lord Himself changes names benignly, and on the basis of events imposes names of special significance, so as to call Abram Abraham (Genesis 17:5), and Sarai Sarah (Genesis 17:15). Also in the Gospel, the former Simon received the name of Peter (Mark 3:16), and the sons of Zebedee are called "sons of thunder" (Mark 3:17) - which is not boanerges, as most people suppose, but is more correctly read benereem.

(Chapter 17—Verse 3 and following) And the Lord spoke to him, saying: Behold, my covenant is with you, and you shall be the father of a multitude of nations, and your name shall no longer be called Abram, but your name shall be Abraham, for I have made you the father of many nations. It should be noted that wherever we read Testament in Greek, in the Hebrew language it is the word covenant or pact, that is, Berith (). The Hebrews say that God, from his name, which is the Tetragrammaton among them, added the letter He to Abraham and Sarah: for he was first called Abram (), which means lofty father, and later he was called Abraham (), which means father of many: for what follows nations is not part of the name, but is understood. It is not surprising, therefore, that when it seems that the letter Α has been added among the Greeks and us: we have called it the Hebrew letter He added; for the language of that tongue is to write with He (ה‎), but to read with A (א‎): just as, on the contrary, the letter A is often pronounced as He.

However, a question arises here which should not be passed over and which may perhaps also, quite independently, be bothering some of you. What does it mean, that when the name of Abraham, this man Jacob’s grandfather, was changed (he was previously called Abram, you see, and God changed his name and said, you shall not be called Abram, but Abraham)? From that time on he was never called Abram. Search in the Scriptures, and you will see that earlier on, before he received another name, he was only called Abram. After he had received the new one, he was only called Abraham. This man Jacob, however, heard the same words when he received another name: You shall not be called Jacob, but you shall be called Israel. Now search the Scriptures, and see how he was always called either name, both Jacob and Israel. When Abram got another name, he was never called anything but Abraham; when Jacob got another name, he was called Jacob and Israel. The name Abraham was to receive its explanation in this world, because it was here that he became the father of many nations, from which his name is derived. The name Israel, on the other hand, belongs to the next world, where we will see God. So the people of God, the Christian people, is in this world and this time both Jacob and Israel; Jacob in our actual situation, Israel in our hopeful expectation.

And you will be the father of many nations, and your name will no longer be called Abram, but you will be called Abraham, because I have made you the father of many nations. Because blessed Abraham left his kin and his father's house at the command of the Lord, he received deservedly also in this gift of reward to exist as the father of many nations; indeed of so many, that not only those who came from his seed according to the flesh, but also those who deriving their origin of flesh elsewhere, would follow the footsteps of his faith and obedience, as the Apostle writes to the Romans with full exposition. It should be known that Abram means Exalted Father, but Abraham means Father of Many, so it is understood, of many nations.