لسان الدين بن الخطيب
In diplomacy, for the first time in Nasrid history he sent an embassy to the Mamluk Sultanate of Cairo. A surviving copy of a letter from the Mamluk Sultan al-Salih Salih indicates that Yusuf had requested military help to fight the Christians; al-Salih prayed for Yusuf's victory but declined to send troops, saying they were needed for conflicts on his own borders. Many of Yusuf's diplomatic exchanges with the rulers of North Africa—especially the Marinid sultans—are preserved in "Rayhanat al-Kuttab" compiled by Ibn al-Khatib.