What is the meaning of: {And his wife was standing, and she laughed. So We gave her good tidings of Isaac, and after Isaac, Jacob}?

The interpretations mention that Sarah, the wife of Abraham (peace be upon him), was standing behind a curtain, listening to the words of the messengers. She laughed, and there is a difference of opinion regarding the reason for her laughter. It was said: she menstruated, or she laughed because fear was removed from her and from Abraham, or she laughed when she saw that the messengers' hands did not reach the food. It was also said: she laughed at the heedlessness of Lot's people, or she laughed out of joy at the good tidings, or in astonishment that she would give birth in her old age and her husband's old age.

Some scholars believe that the verse contains a reordering of words (taqdim wa ta'khir), so the meaning is: "And his wife was standing, so We gave her good tidings of Isaac, and after Isaac, Jacob, so she laughed." This is because Abraham prayed to his Lord to grant him a child, but his prayer was delayed until he became old. Then the angels came to give Sarah the good tidings of her son Isaac, and after him Jacob. So Abraham praised his Lord for having granted him Ishmael and Isaac in his old age.