Perhaps some Bible bloggers will respond...
As disturbingly shown by Caravaggio's painting "The Sacrifice of Isaac," Abraham is often taken as a symbol of powerful faith because he was willing to sacrifice his own son Isaac at God's command even though God had promised to make Abraham a great nation through Isaac. Presumably, God would somehow follow through on the promise even after Isaac's death.
The story is a profoundly troubling one even if -- or rather because -- it demonstrates the depth of Abraham's faith.
Perhaps this sacrifice story lies behind Paul's emphasis upon Abraham's never-weakening faith in God. But that raises a question. Yesterday, a few others and I were trying to figure out why Paul states that Abraham never wavered in his faith in God, not even when promised a son through Sarah:
The Epistle of Paul the Apostle to the Romans
4:18 [Righteousness is imputed to those with the faith of Abraham, w]ho in hope believed against hope, to the end that he might become a father of many nations, according to that which had been spoken, So shall thy seed be. 4:19 And without being weakened in faith he considered his own body now as good as dead (he being about a hundred years old), and the deadness of Sarah's womb; 4:20 yet, looking unto the promise of God, he wavered not through unbelief, but waxed strong through faith, giving glory to God, 4:21 and being fully assured that what he had promised, he was able also to perform. 4:22 Wherefore also it was reckoned unto him for righteousness.
This assertion seems at odds with Genesis 17:15-19, which appears to show Abraham wavering (shown below in red font; ignore the green font for the moment):
A Hebrew-English Bible According to the Masoretic Text and the JPS 1917 Edition
טו וַיֹּאמֶר אֱלֹהִים, אֶל-אַבְרָהָם, שָׂרַי אִשְׁתְּךָ, לֹא-תִקְרָא אֶת-שְׁמָהּ שָׂרָי: כִּי שָׂרָה, שְׁמָהּ
15 And God said unto Abraham: 'As for Sarai thy wife, thou shalt not call her name Sarai, but Sarah shall her name be.
טז וּבֵרַכְתִּי אֹתָהּ, וְגַם נָתַתִּי מִמֶּנָּה לְךָ בֵּן; וּבֵרַכְתִּיהָ וְהָיְתָה לְגוֹיִם, מַלְכֵי עַמִּים מִמֶּנָּה יִהְיוּ
16 And I will bless her, and moreover I will give thee a son of her; yea, I will bless her, and she shall be a mother of nations; kings of peoples shall be of her.'
יז וַיִּפֹּל אַבְרָהָם עַל-פָּנָיו, וַיִּצְחָק; וַיֹּאמֶר בְּלִבּוֹ, הַלְּבֶן מֵאָה-שָׁנָה יִוָּלֵד, וְאִם-שָׂרָה, הֲבַת-תִּשְׁעִים שָׁנָה תֵּלֵד
17 Then Abraham fell upon his face, and laughed, and said in his heart: 'Shall a child be born unto him that is a hundred years old? and shall Sarah, that is ninety years old, bear?'
יח וַיֹּאמֶר אַבְרָהָם, אֶל-הָאֱלֹהִים: לוּ יִשְׁמָעֵאל, יִחְיֶה לְפָנֶיךָ
18 And Abraham said unto God: 'Oh that Ishmael might live before Thee!'
יט וַיֹּאמֶר אֱלֹהִים, אֲבָל שָׂרָה אִשְׁתְּךָ יֹלֶדֶת לְךָ בֵּן, וְקָרָאתָ אֶת-שְׁמוֹ, יִצְחָק; וַהֲקִמֹתִי אֶת-בְּרִיתִי אִתּוֹ לִבְרִית עוֹלָם, לְזַרְעוֹ אַחֲרָי
19 And God said: 'Nay, but Sarah thy wife shall bear thee a son; and thou shalt call his name Isaac; and I will establish My covenant with him for an everlasting covenant for his seed after him.
If Paul thinks that this doesn't show Abraham wavering in his faith, then he must have some way of interpreting the text in a different sense. Now, Paul probably used the Septuagint (Greek) version of the Old Testament, and one of the men yesterday who was discussing Paul's view mentioned that the Greek verb used for laughed in verse 17 can mean "laughed in joy" -- which would probably explain why Calvin took the passage to have this meaning. (Sorry not to supply references here, but the semester has begun.) So, Paul might have assumed on the basis of the Septuagint that the laughter was not a sign of disbelief.
But suppose that Paul was also looking at the Hebrew (and could read it). Could he have read it a different way?
Now comes the sheer speculation ... and the green font.
The verbs in Genesis 17:16 use the past tense form (perfect) but are read as future meanings due to the vav-consecutive, which switches tenses. Thus:
וְגַם נָתַתִּי מִמֶּנָּה לְךָ בֵּן
and moreover I will give thee a son of her
Yet, the vav is not placed directly before the verb, so could one (mis)read this as having a past meaning?
and moreover I have given thee a son of her
Suppose that Paul interpreted the passage as showing Abraham struck by the ambiguity of this promise -- was it past or future? Paul could then argue that Abraham was not wavering but misunderstanding and laughing at what he (Abraham) considered an absurd interpretation of what God was saying.
To spell it out ... Abraham sees the ambiguity of וְגַם נָתַתִּי and laughs to imagine the absurdity of thinking that this might be a future promise (and moreover I will give). He then takes it as refering to a past event, the birth of Ishmael (and moreover I have given). He therefore asks God's blessing on Ishmael. God then corrects Abraham's understanding by clarifying that the promise is a future one and that Ishmael is not the promised child.
Now, one might point out that since Ishmael is not Sarah's son, then Paul could not have read Abraham to be misunderstanding God as referring to Ishmael, for that child had been born to Sarah's servant, Hagar.
Here, though, one need only recall Genesis 16:2, which shows Sarai (Sarah) urging Abraham to sleep with Hagar in order that Sarai might build up a family through Hagar. According to custom, or so the verse implies, the child through Hagar would be considered a child of Sarai.
If Paul did read the Genesis passage (17:15-19) in this way, then he could argue that Abraham was not wavering in disbelief but simply misunderstanding God's meaning and that when God corrected Abraham's misunderstanding, then Abraham believed in the promise of a future son.
Well, as I said, sheer speculation ... but if somebody could find a rabbinical text proposing the same thing...