Do not wish to meet the enemy, and ask Allah for well-being

It is narrated from Sayyiduna Jabir bin Abdullah (may Allah be pleased with him) that he said: On the day of Khaybar, the Messenger of Allah (peace and blessings be upon him) sent a man (with the banner), but he showed cowardice and came back. Then Sayyiduna Muhammad bin Maslamah (may Allah be pleased with him) came and said: "O Messenger of Allah! I have never seen (a sight) like today; (his brother) Mahmud bin Maslamah has been martyred." The Messenger of Allah (peace and blessings be upon him) said: "Do not wish to meet the enemy, and ask Allah for well-being, for you do not know how you will be tested with them. But when you do meet them, say: 'Allahumma anta rabbuna wa rabbuhum, wa nawasina wa nawasihim biyadik, wa innama taqtuluhum anta' (O Allah, You are our Lord and their Lord, our forelocks and their forelocks are in Your hand, and it is only You who kills them). Then keep firmly seated on the ground, and when they come upon you, rise up and call out 'Allahu Akbar'." Then the Messenger of Allah (peace and blessings be upon him) said: "Tomorrow I will give the banner to a man who loves Allah and His Messenger, and Allah and His Messenger love him; he will not turn his back and flee, and Allah will grant victory at his hands." The people began craning their necks in hope of this honour, while Sayyiduna Ali (may Allah be pleased with him) was suffering from an eye ailment in those days. The Messenger of Allah (peace and blessings be upon him) said to him: "Go forward." He said: "O Messenger of Allah! I cannot see anything." So he (peace and blessings be upon him) put his saliva in his eyes, prepared the banner for him and handed it to him. Sayyiduna Ali (may Allah be pleased with him) said: "O Messenger of Allah! On what basis shall I fight them?" He (peace and blessings be upon him) said: "On the basis that they bear witness that there is no god but Allah and that I am the Messenger of Allah. When they accept this, they will have protected their blood and their wealth from me, except by their due right, and their reckoning rests with Allah, the Mighty and Majestic." The narrator says: Then he met the enemy, and Allah granted victory at his hands.
The two Shaykhs agreed on (recording) the basis of the hadith of the banner, but they did not record it with this wording.

Iyas bin Salamah narrates from his father, Sayyiduna Salamah bin al-Akwa' (may Allah be pleased with him), that he said: We were present with the Messenger of Allah (peace and blessings be upon him) at the battle of Khaybar, when the Messenger of Allah (peace and blessings be upon him) put his saliva in the eyes of Sayyiduna Ali (may Allah be pleased with him) and he was cured. Then he (peace and blessings be upon him) gave him the banner. Then Marhab (the enemy's champion) came out reciting these verses: "Khaybar knows well that I am Marhab, armed to the teeth, a seasoned hero; when wars blaze up, I too become a flame." So Sayyiduna Ali (may Allah be pleased with him) came out against him saying: "I am the one whose mother named me Haydar (lion), like the lion of the forests, fearsome to behold; I will repay you with a great measure (sandarah) for a sa'." The narrator says: Then he struck Marhab such a blow that he split his head open and killed him, and thus victory was granted.
This hadith is sahih (authentic) on the condition of Imam Muslim, but they did not record it with this wording.