It is narrated from Abdullah bin Umar (may Allah be pleased with them both) that a man came to the Prophet (ﷺ) and asked him: "What clothes should a Muhrim (one in the state of Ihram) wear?" The Prophet (ﷺ) said to him: "A Muhrim should not wear a shirt, nor a turban, nor a cap, nor trousers, nor socks, but whoever does not have sandals may wear socks after cutting them below the ankles."
Hadith Referenceمسند الإمام الشافعي / كتاب الحج / 839
Hadith Takhrijاخرجه البخاري، العلم، باب من أجاب السائل بأكثر مما سأله (134) ومسلم، الحج، باب ما يباح للمحرم بحج أو عمرة البسمة الخ (1177)۔