It is narrated from Sayyidah Su'da or Asma' (may Allah be pleased with her) that the Prophet (peace and blessings be upon him) came to Sayyidah Duba'ah bint al-Zubayr bin Abd al-Muttalib (may Allah be pleased with her) and said to her: "O aunt, perform Hajj." She said: I am a heavy (bodied) woman, and I fear being prevented. He ((peace and blessings be upon him)) said: "Perform Hajj, and make the condition that I will leave the state of ihram wherever I am prevented."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21143