Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) narrates: When we were facing the enemy with the Prophet (peace and blessings be upon him), each one of us, when stepping forward into the row for fighting, would watch over his brother's knee more carefully than over an arrow when it is shot. He would say: "Watch your knee, for I am seeking (martyrdom) just as you are seeking it." Allah Almighty has said: "As though they were a solid structure."
Imam al-Tabarani recorded this narration in al-Mu'jam al-Awsat. Its chain contains a narrator, Abu Harun al-Abdi, and he is matruk (abandoned). The hadith of Sayyiduna Abu Umamah (may Allah be pleased with him) has already passed at the end of the chapter on the virtue of jihad, concerning the virtue of a man standing in the row in the path of Allah.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الجهاد / 9670