The saying of Allah Almighty: "And if you are in a state of janabah, then purify yourselves thoroughly." [Surah al-Ma'idah: 6]
And in the hadith of Sayyiduna Imran bin Husayn (may Allah be pleased with him), the Messenger of Allah (peace and blessings be upon him) said to the junub man: "Go and pour it (the water) over yourself."
And in the hadith of Sayyiduna Abu Dharr (may Allah be pleased with him) he said: "When you find water, let it reach your skin."
And he (peace and blessings be upon him) did not order him to observe any sequence (in the bath).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / Q870
It is narrated from Sayyiduna Abu Dharr (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Clean earth is the means of ablution for the Muslim, even if he does so for ten years; and when he finds water, let him pour it over his body, for that is better."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 870