The Butler, Commending is Chapter 127 of the Kuroshitsuji manga.
The assailant shoots Soma Asman Kadar's hand. Enraged, Agni lunges at the assailant, but the latter stabs his side. They continue fighting, with Agni stunned by the assailant's speed and strength. When the assailant aims for Soma again, Agni shields Soma, taking the bullet in his place. Agni, then, reflects on his friendship with Soma, calling Soma "his sun," as he drags Soma to safety, while the assailant knifes him. He pushes Soma into a room, and holds the door shut. Soma begs him to open the door, but he stays put, and tells him that he was happy being his butler, just as the assailant attacks him from behind.
Later, Ciel Phantomhive and Sebastian Michaelis arrive at the London townhouse, where Sebastian notices that something is amiss. They enter the house, and are astonished to find blood and rubble. They follow the trail of blood, and find Agni at the door, with a multitude of knives in his back. After examining Agni, Sebastian reports to Ciel that he is not breathing, to Ciel's shock. Sebastian is, then, forced to break open the door, where he discovers Soma sobbing.
Sebastian sets Agni down, and states that, for prioritizing Soma's safety and happiness, Agni is "the very epitome of a butler."