What is the ruling on someone who forgets a piece of underwear after entering a state of Ihram for Hajj or Umrah, and what is incumbent upon them? And what is the ruling on someone who passes through the Hajar Isma'il (Hijr Ismail) during Tawaf with the intention of avoiding the crowd, and what is incumbent upon them?

If a pilgrim in the state of ihram wears sewn clothing out of forgetfulness or ignorance, some scholars hold that there is no sin upon him and no expiatory offering (fidyah). He must remove it immediately upon remembering or realizing, otherwise the expiatory offering becomes obligatory upon him. As for circumambulating inside the Hijr, it invalidates the circuit, because the Hijr is part of the House (Kaaba). If the flaw was in the Ifadah circumambulation for Hajj, you must return to Mecca and circumambulate seven times, and repeat the Sa'i if it was not performed after a valid Tawaf al-Qudum. If the flaw was in the Tawaf al-Qudum, nothing is required of you because it is a Sunnah. However, if it was in the farewell circumambulation (Tawaf al-Wada'), you must sacrifice a sheep within the sacred precinct (Haram).