A very interesting question that concerns also the somewhat tricky matter of the so-called ‘Bible contradictions’, as we will see soon.
I will not give here a full answer, since the arguments of Dottard and Rhetorician seems to me well sounded and convincing.
In fact, Dottard well pointed the different kinds of ‘laughter’ and added the keen comments reported by a number of Bible scholars. For his part, Rhetorician well explained how the different God’s reaction to the ‘laughter’ of some of his servants helps us to distinguish the above mentioned kinds of ‘laughter’ (disbelief [any degree], or other kind of feelings).
Moreover, the arguments focusing on the comparison between Rom 4:19-20 and the story of Abraham & Sarah seems forceful to me. Of the same import it seems to me the chronological sequence of the events described in the 17th and 18th chapters of Genesis.
Though the verses 22-27 of Genesis 17 do not directly report Abraham doing that, surely he told his wife the promise God had sworn to him, which concerned also her (Gen 17:2 [“I will multiply you…”]; 17:5-6 [“I will make you a father of many nations…”]; 17:7-10 [“…your offspring…”]; 17:16, 19, 21 [“I will give you a son by her…”]. So, the visit of some God’s representatives at Mamre (Gen 18) was not an entirely unexpected event for the couple.
Moreover, Abraham – in some manner – recognized that the ‘men’ (Gen 18:2) were not simple humans asking for shelter. In fact, he recognized from the start that the ‘men’ were special representatives of God sent by Him.
Here, a lot of Bible translations – in Gen 18:3 – have “Lord” instead of “Yahweh”. But, we have to remember – I’ve yet mentioned this data elsewhere - that this passage is the first of the 134 changes the Sopherim (ancient [Hebrew] Bible scribes) operated (see Christian David Ginsburg, in The Massorah, Ktav Publishing House, New York, 1975 [reprint], vol. I, pages 25-26, § 115; IV, page 28, § 115).
Besides that, the context itself (Gen 18:13, 14, 17, and so on) indicates us that the “Lord” of Gen 18:3 was – vicariously – Yahweh (“the Judge of all the earth”, Gen 18:25). Then, we can conclude that the Sarah’s ‘laughter’ did not depend on the fact the she did not recognized the men as special representatives of Yahweh.
As regards Agarza, I well see his trouble. On the one hand, he understand - according me - that the reaction of the man/angel to the ‘laughter’ of Sarah (“And the LORD [יהוה] said unto Abraham ‘Wherefore did Sarah laugh, saying: Shall I of a surety bear a child, who am old? Is any thing too hard for the LORD [יהוה]. At the set time I will return unto thee, when the season cometh round, and Sarah shall have a son.’” - Gen 18:13-14 [JPS]) demonstrates without any doubt a degree of lack of faith by Sarah herself.
On the other hand, Agarza is worried because the inspired words of Paul in Hebrew 11:11 seem to exclude also a minimum degree of disbelief from Sarah’s part.
Really – instead – there’s no reason to consider these two Bible texts in contradiction each other. Why?
The Paul’s talk about the faith demonstrated by a number of God’s servants (Heb 11:4 – 12:1) speaks about the final judgement of God about them. In other words, Yahweh (“the Judge of all the earth”, Gen 18:25) taking into account every aspect of the life of those servants of Him decided they were “witnesses” [μαρτύρων] (Heb 12:1), being approved by Him (Heb 11:39-40).
But, this does not means – necessarily - that in every moment of their life those servants had faith, or that they did not always waver from their faith. This is not a speculation, but a Bible teaching.
In Heb 11:24, 27, 28 Paul spoke about Moses and the faith he demonstrated (see how Paul applied three times the expression “by faith” to Moses behaviour). This means Moses did cannot – necessarily – have, never, a wavering of his faith?
Please, read Num 20:12 (bold is mine): “Jehovah later said to Moses and Aaron: ‘Because you did not show faith in me and sanctify me before the eyes of the sons of Israel, you will not bring this congregation into the land that I will give them.” (NWT)
In conclusion, though Moses – in one occasion – had no (enough) faith in God, and this fact did cost him the entrance in the Good Land, the final judgement of God was that Moses was considered deserving to be numbered among the “witnesses” [μαρτύρων] (Heb 12:1) of faith.
In a similar way, Sarah…
So, not only this explanation proves that there is not contradiction in the Bible passages we are discussing on, but also it emphasizes the Yahweh God’s splendid quality king David expressed in a Psalm (103:10):
“He does not deal with us according to our sins, nor repay us according to our iniquities” (ESV)