Salama bin Akwa reported,

We set out with the Prophet ﷺ toward Khaybar, traveling by night. A man from the company said to Amir, "Amir, will you not let us hear some of your verses?" Amir was a man known for his camel-driving songs, so he dismounted and began chanting to urge the camels along, saying:O Allah, were it not for You, we would not have been guided, nor given charity, nor prayed. So forgive us, may we be ransom for You, for whatever sins we have committed, and make our feet firm if we meet the enemy, and send down tranquility upon us. Truly, when we are called out against, we refuse, and with shouting they have come down upon us.The Messenger of Allah ﷺ asked, "Who is this driver?"They said, "Amir bin al-Akwa."He said, "May Allah have mercy on him."A man from the company said, "It is now certain, Prophet of Allah. If only you had let us benefit from him longer."Then he mentioned the rest of the hadith, in which it is said, When the two sides drew up in ranks, Amir's sword was short. He reached out with it to strike the leg of a Jewish fighter, but the edge of his sword rebounded and struck the joint of his own knee, and he died from it.When they returned, Salama said, The Messenger of Allah ﷺ saw me, and he took me by the hand and asked, "What is the matter with you?"I said to him, "May my father and mother be your ransom. They are claiming that Amir's deeds have been wasted."The Prophet ﷺ said, "Whoever says that has lied. He has two rewards," and he joined two of his fingers together, "He was a striver and a warrior. Few Arabs have walked the earth like him."

عن سلمة بن الأكوع قال

خرجنا مع النبي ﷺ إلى خيبر، فسرنا ليلا، فقال رجل من القوم العامر: يا عامر، ألا تسمعنا من هنيهاتك؟ وكان عامر رجلا حداء، فنزل يحدو بالقوم يقول: اللهم لولا أنت ما اهتدينا ولا تصدقنا ولا صلينا فاغفر فداء لك ما اتقينا وثبت الأقدام إن لاقينا وألقين سكينة علينا إنا إذا صيح بنا أبينا وبالصياح عولوا علينا فقال رسول الله ﷺ: من هذا السائق؟ قالوا: عامر بن الأكوع. قال: يرحمه الله قال رجل من القوم: وجبت يا نبي الله، لولا أمتعتنا به؟ فذكر الحديث وفيه: فلما تصاف القوم كان سيف عامر قصيرا، فتناول به ساق يهودي ليضربه، ويرجع ذباب سيفه، فأصاب عين ركبة عامر، فمات منه. قال: فلما قفلوا، قال سلمة: رآني رسول الله ﷺ وهو آخذ بيدي، قال: ما لك؟ قلت له: فداك أبي وأمي، زعموا أن عامرا حبط عمله؟ قال النبي ﷺ: كذب من قاله، إن له لأجرين-وجمع بين إصبعيه- إنه لجاهد مجاهد، قل عربي مشى بها مثله.