Answer: What necessitates repeating the Farewell Tawaf, if one delays after it, is intending to remain—even for an hour—for something other than the exceptions mentioned.
It is understood from the author’s words that once a person has performed the Farewell Tawaf, he should not walk backwards when he wishes to leave the mosque. Walking backwards means retreating backward; nor should he stand at the door, say the takbir three times, and say, “Peace be upon you, O House of Allah.” All of this is religious innovation. Once you have performed the Farewell Tawaf, proceed on your way, with your back to the Ka‘bah, and there is nothing blameworthy upon you. Venerating the Ka‘bah is only through following what has been reported from the Prophet ﷺ. He would not walk backwards when he wished to leave, nor would he stop upon reaching the mosque door, look at the Ka‘bah, and bid it farewell.
His words, “If someone other than a menstruating woman omits it, he must return to it,” mean that he is required to return and perform tawaf. If a menstruating woman omits it, however, she is not required to return—unless she becomes pure before leaving the built-up area of Mecca, in which case she must return. But if she becomes pure after leaving the built-up area, even by a small distance—even while still within the Sacred Precinct—she is not required to return.
The evidence for this is the statement of Ibn ‘Abbas: “Except that concession was granted to the menstruating woman” (1). The woman experiencing postnatal bleeding is treated likewise.
His words, “If returning is difficult, or if he does not return, then he must offer a sacrificial animal,” mean that if returning is difficult and he does not return, he must offer a sacrificial animal. Likewise, if he does not return despite there being no difficulty, he must offer a sacrificial animal. The difference, however, is that if he omits it due to hardship, the sacrifice is due from him but he incurs no sin; whereas if he omits it without hardship, the sacrifice is due from him along with sin, because he deliberately abandoned an obligation.