Then the year 204 AH began.
In that year:
Al-Maʾmun arrived in the lands of Iraq. He had passed through Jurjan, where he stayed a full month, and then set out from there, and (1) at each halting-place he would remain a day or two. He came to al-Nahrawan and stayed eight days. Earlier he had written to Tahir ibn al-Husayn, who was in al-Raqqah, ordering him to meet him at al-Nahrawan; Tahir did so, and the principal men of the House, the commanders, and the bulk of the army came out to receive the caliph. On the following Saturday he entered Baghdad in mid-morning, with fourteen nights remaining in Safar, in great pomp and with a mighty host. He, all his companions and youths, and all their garments were in green, and the people of Baghdad and the whole of Banu Hashim likewise donned green.
Al-Maʾmun first lodged in al-Rusafa, then moved to his palace on the Tigris. The amirs and dignitaries of the state began to visit his residence as was their custom. The Baghdadis had changed their dress to green and were burning everything they found of black; in that condition they remained for eight days. Thereafter he examined the petitions of Tahir ibn al-Husayn, whose very first request was that they return to wearing black, for it was the attire of his forefathers, the dynasty of the heirs to the Prophets.
On the next Saturday, the twenty-third of Safar, Al-Maʾmun sat in audience still wearing green. Then he ordered a black robe of honor (2) and placed it on Tahir ibn al-Husayn; (3) after him he arrayed a number of the commanders in black. The people therefore resumed black and returned to it, once he had seen their obedience and readiness to comply.
It is also said that Al-Maʾmun continued to wear green for twenty-nine nights after entering Baghdad; Allah knows best.
When his uncle Ibrahim ibn al-Mahdi came to him after hiding for six years and some months, Al-Maʾmun said to him, “You are the black caliph.” Ibrahim set about apologizing and seeking forgiveness, saying, “I am the one upon whom you have bestowed pardon,” and he recited to Al-Maʾmun on that occasion:
Black does not disgrace the noble-souled man,
nor the cultured, courteous youth;
(4) If blackness has a share allotted to you,
then the whiteness of character is my share.
Judge Ibn Khallikan (5) said: One of the later poets, Nasr Allah (6) ibn Qalaqis al-Iskandari, versified the same idea, saying: