He used to dislike consuming unripe dates on their own and would say, "The Messenger of Allah ﷺ forbade the delegation of Abdul-Qays from muzzaa," and he feared that this might refer to unripe dates.
حدثنا بهز حدثنا همام أخبرنا قتادة عن عكرمة
كان يكره البسر وحده ويقول نهى رسول الله ﷺ وفد عبد القيس عن المزاء فأرهب أن تكون البسر
Its isnad is sahih, see also 2476. Al-Mizaa, with a dammah on the meem, a doubled zay, and a long vowel. Ibn Athir said regarding the hadith, "Beware, al-mizaat are forbidden," meaning wines, which is the plural of mizzah, that is, wine that has some sourness in it, also called al-mizaa with the long vowel. It is also said that it is made from mixing unripe and ripe dates. This is the source of the hadith, "I fear that al-mizaa which I forbade to Abdul-Qays is this." It is on the pattern of fiala, from mazaazah, or on the pattern of fiaal from al-mazz, meaning excess. He means that al-mizz, with a kasrah on the meem and a doubled zay, means excess, as one says, "This thing has a mizz over that," meaning an excess. In Lisan it says, al-mizaa is wine with a delicious taste, so named because of the way it stings the tongue.