Ibn Umar (may Allah be pleased with them both) said: "It is part of the Sunnah that a person takes a ritual bath (ghusl) for ihram, and also when entering Makkah."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 8946
Hadith Gradingمحدثین:حسن لغيره
Hadith Takhrij«حسن لغيره۔ مستدرك حاكم 1/ 610۔ دارقطني 2/220»