Although he was renowned in the eastern Islamic world as a scholar, his reign was characterized by violence and instability, and Saffarid rule over Sistan came to an end with his deposition.

Khalaf was born in the middle of November 937 to Abu Ja'far Ahmad and Banu, a daughter of the second Saffarid amir, Amr ibn al-Layth in Sistan.

Soon afterward he led an army against Zarang, which was under the control of a rival Saffarid named Abu Hafs b. Muhammad.

On the way home he stopped at Baghdad, where the Buyid amir Mu'izz al-Dawla gave him an audience with the Abbasid caliph al-Muti.

Khalaf felt, however, that Abu'l-Husayn Tahir would not willingly give up control of Sistan upon his return, so he went to the Samanids for assistance and received an army.

[citation needed] Within a year of the death of Abu'l-Husayn Tahir, his son Husayn pressed his claim to the amirate.

Khalaf retook Zarang in April 971 and immediately began to root out Husayn's supporters in the city, causing many of them to flee to Khurasan.

Khalaf's forces attempted numerous sorties but were unable to break the siege; the Samanid and Saffarid armies battled each other several times, with neither gaining a decisive victory.

The Samanid amir eventually sent a member of the Simjurid family, Abu'l-Hasan Muhammad Simjuri, to break the stalemate.

These had been virtually lost to the Saffarids during Abu'l-Husayn Tahir's rule; the local Turks had been more or less independent before the Ghaznavid Sebuktigin conquered the region in c. 978.

Khalaf is reported to have participated in a campaign together with Sebuktigin and the Farighunid amir of Guzgan to assist the Samanids in quelling a rebellion in Khurasan.

Khalaf viewed this as an opportunity to gain territory from the Ghaznavids, and sent his fourth son Tahir to take Quhistan and Badghis in 998.

Khalaf's son Tahir is mentioned as having invaded Buyid Kerman in 1000, although he was ultimately unsuccessful in making any lasting gains.

After Tahir died, the commander of his army sent a message to Mahmud of Ghazna, stating that the people of Zarang wanted him to become the ruler of Sistan.

Khalaf resisted, barricaded himself in Taq and withstood a siege by the Ghaznavid force, so Mahmud decided to come personally in November 1002.

Rumors that Khalaf was in contact with the Karakhanids, whom Mahmud was at war with at the time, resulted in him being transferred south to Gardez, where he died in 1009.