Ibn Zubayr used to give us dates as our ration. People at that time were suffering hardship, and we would be eating when Ibn Umar would pass by us. He would say, "Do not eat dates two at a time, for the Messenger of Allah ﷺ forbade taking two together unless one asks his companion's permission."
كان ابن الزبير يرزقنا التمر، قال: وقد كان أصاب الناس يومئذ جهد، وكنا نأكل فيمر علينا ابن عمر ونحن نأكل، فيقول: لا تقارنوا فإن رسول الله ﷺ نهى عن الإقران، إلا أن يستأذن الرجل أخاه.
Bukhari narrated it in the Book of Foods (5446), and Muslim narrated it in the Book of Drinks (2045: 150), both through the route of Shuba, who said, "I heard Jabala bin Suhaym say," then he related it. Shuba's statement, "I do not think this phrase..." meaning the requirement of asking permission, is inserted from Ibn Umar's own words and is not a raised (marfu) statement.However, Muslim also narrated it right after through the route of Sufyan (that is, Thawri) from Jabala bin Suhaym, who said, "I heard Ibn Umar say, the Messenger of Allah ﷺ forbade a man from combining two dates together until he asks permission of his companions." This apparently indicates that there is no insertion, though the possibility remains, as Hafiz mentioned in Fath al-Bari (9/571), following Thawri, and citing as corroboration for Ibn Umar's account the hadith of Abu Hurairah, which is clearly marfu. He concluded that there was no insertion. Bukhari did the same in other places in his Sahih, where he relied on this addition and used it as a heading in the Book of Wrongs and the Book of Partnership.Hafiz said, "It does not necessarily follow, just because Ibn Umar mentioned the permission on one occasion without raising it to the Prophet, that his basis for it was not something raised to the Prophet. It has been reported that he was asked for a ruling on this matter and he gave a ruling, and the one giving a ruling may not always trouble himself to explain the basis of his ruling..."The scholars have differed regarding the reason combining dates was forbidden. Some said it was because doing so shows greed and covetousness that disgraces the one who does it. Others said it was because it involves cheating and wronging one's companions. Still others said they were forbidden from it only because of how harsh their living conditions were and how scarce things were. All of these are possible explanations, so the guidance to ask permission came because of the goodwill it fosters toward others, and this was later abrogated once conditions became more abundant. For more, see Fath al-Bari (9/571–572).I say, it has also been reported in a version from Burayda bin Husayb, who said, the Messenger of Allah ﷺ said, "We used to forbid you from combining dates, but now combine them, for Allah has expanded what is good." Bazzar narrated it in Kashf Astar (2884), and Tabarani narrated it in Awsat (7064), both through the hadith of Yazid bin Bazi, from Ata Khurasani, from Abdullah bin Burayda, from his father, relating it.Bazzar said, "We do not know of any route for it from Burayda except this one, and we do not know of anyone who narrated it except Adam (Ibn Abu Iyas) from Yazid."I say, it is not as he said, for Tabarani narrated it from Mahbub Attar, from Yazid, with the same chain of transmission, except that he added "Abu Khalid" between Yazid and Ata. Yazid bin Bazi is daif, having been declared daif by Ibn Main, Daraqutni, and others, and Haythami cited this weakness in Majma (5/41).