Nafi' (may Allah have mercy on him) says that Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) was coming from Makkah, and when he reached the place called Qudayd, some news reached him from Madinah, so he turned back and entered Makkah without ihram.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9844
Imam Malik (may Allah have mercy on him) narrates from Ibn Shihab (may Allah have mercy on him) that he was asked about a man who enters Makkah without ihram. He said: I do not see any harm in that.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9845
Abdullah bin Abi Qatadah was informed by his father that he took part with the Prophet (peace and blessings be upon him) in the expedition of Hudaybiyah. (He said:) Everyone except me entered ihram for Umrah. I hunted a wild ass and fed it to my companions, who were in ihram. Then I came and informed the Prophet (peace and blessings be upon him) that we had some meat left over. He (peace and blessings be upon him) said: "Eat it," while they were all in ihram.
(b) Abu Muhammad, the freed slave of Abu Qatadah (may Allah be pleased with him), narrates from Abu Qatadah (may Allah be pleased with him): We set out with the Messenger of Allah (peace and blessings be upon him), and when we reached the place called al-Qahah, some of us were in ihram and some were not.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9846