The verse says...

“And his wife was standing (by) and she laughed when We gave her the glad tidings (of the birth) of Isaac, and after Isaac, of Jacob.” There are several possibilities mentioned as to the reasons for the standing by of Abraham’s wife; when the verse says: “And his wife was standing (by) and she laughed when We gave her the glad tidings (of the birth) of Isaac, and after Isaac, of Jacob.” a- for worshipping b- for serving the guests c- for witnessing the comings and goings of individuals and the discussions.

Her laughter was either because she understood that their abstinence from eating was not a sign of danger for Abraham, or, as has been pointed out in some commentaries, Sarah, Abraham’s wife, was an elderly woman who had long passed her child bearing days when she suddenly heard this unbelievable news. However, while in this mood, she realized that the Divine Will was that she would have a child. However, each group of the Divine angels were commissioned to accomplish a particular affair.

These group of angels followed two objectives. One of which was the extermination of the corrupt people of Lot, and the other was to give the good tidings of a child to be bestowed upon Abraham (as) and Sarah. Surah Hud – Verse 72 قَالَتْ يَا وَيْلَتَي ءَأَلِدُ وَأَنَاْ عَجُوزٌ وَهَذَا بَعْلِي شَيْخاً إِنَّ هَذَا لَشَيْءٌ عَجِيبٌ 72. “She said: ‘Voe is me! Shall I bear a child when I am an old woman, and this my husband is an old man?

Verily this is a wonderful thing!’” Sarah, who had given up hope of having children, with a tone of tremendous wonder, exclaimed implying that alas for her. Might she give birth to a child despite her old age and despite the fact that her husband too was old? That was a truly amazing matter. The verse itself says: “She said: ‘Voe is me! Shall I bear a child when I am an old woman, and this my husband is an old man?