Sayyiduna Ibn Umar (may Allah be pleased with them both) said: "It is the Sunnah for a man to take a ritual bath (ghusl) when entering ihram and when entering Makkah."
Imam al-Tabarani (may Allah have mercy on him) said: "No one narrated this hadith from Bakr (may Allah have mercy on him) except Humayd, and Sufyan bin Habib is alone in narrating it."
Hadith Referenceالمعجم الأوسط / باب الميم / 8046
Hadith Takhrij«أخرجه مالك فى «الموطأ» برقم: 1152، والبزار فى «مسنده» برقم: 6158، وابن أبي شيبة فى «مصنفه» برقم: 15847، 15850»