In that same year al-Rashid entrusted every affair of the caliphate to Yaḥyā ibn Khālid ibn Barmak.

In it as well, al-Walīd ibn Ṭarīf rose in rebellion in al-Jazīrah, assumed authority there, and killed a great many of its inhabitants; he then marched on to Armenia, and regarding his fate we shall speak in due course.

That year al-Faḍl ibn Yaḥyā set out for Khurāsān. He governed the province with excellence, built ribats and mosques, campaigned beyond the River Oxus, and from among the non-Arabs raised an army which he called al-ʿAbbāsiyyah, binding their allegiance to himself. They numbered some five hundred thousand men. About twenty thousand of them he dispatched to Baghdad, where they became known as the Karnabiyyah.

Concerning this Marwān ibn Abī Ḥafṣah said:
Al-Faḍl is but a shooting star that never fades,
When battle rages and the lesser stars grow dim.
He guards the realm of folk whose rightful share is slight,
Yet still a line of heritage remains within their grasp.
At the command of the sons of the Pilgrims’ Water-Bearer
Stand legions that seek no cause but theirs alone.
Battalions for the House of al-ʿAbbās—
Both Persian and Arab know the order Faḍl has forged.
You fixed five hundred thousand in their ranks
From the myriad hosts the registers record.
They fight for those who, if lineage be traced,
Are nearest to Aḥmad, as the Furqān attests.
Indeed the generous son of Yaḥyā, al-Faḍl, lets
No silver or gold remain upon his open palms.
Not a day has passed since first he girded his belt
But that a company grew rich through what he gave.
How many heights of bounty and of valor he has won—
Aspirants grow weary long before they reach such ends.
He grants largesse when even the liberal hold back,
Nor does he falter when the Indian blades are drawn.
Neither pleasure—whose sole end for him is Allah—
Nor anger leads him save to what is true.
Your kindness overflows so fully that
No saving rain, no boundless sea can match its tide.

Marwān had also recited to him before his departure for Khurāsān:
Have you not seen that generosity, from Adam’s very hand,
Has flowed until it rested in Faḍl’s palm?
Whenever Abū al-ʿAbbās’ sky pours forth,
Behold the torrent, witness the downpour!

He further said of him:
When a mother is alarmed by her child’s hunger,
She calls upon al-Faḍl’s name and the child is stilled.
Through you, O Yaḥyā, Islam is strengthened—
Even your youngest is already full-grown.

He concluded, and al-Faḍl ordered that he be given one hundred thousand dirhams; Ibn Jarīr has related the report.

Salm al-Khāsir likewise said of them:
How could one fear hardship in a land
Where the very seas live beside the Barmakids?