Salim (may Allah have mercy on him) said: Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) used to reject making a stipulation in Hajj and would say: "Is not the Sunnah of the Messenger of Allah (peace and blessings be upon him) sufficient for you? If one of you is held back from Hajj, he should perform tawaf of the House and (the sa'i of) al-Safa and al-Marwah, then he leaves ihram from everything until he performs Hajj the following year, and he should offer a sacrificial animal, or fast if he does not find one." Yunus said: Rabi'ah said: We do not know of any stipulation that is permissible in one's ihram.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10123