Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Abu Sa'id Khudri, may Allah be pleased with him, that the Messenger of Allah, peace and blessings be upon him, said: "The best jihad in the sight of Allah Almighty is of those people who stand in the first row facing the enemy and do not turn back until they are martyred. These are the people who will enter the highest chambers of Paradise. Your Lord looks towards them, and when your Lord smiles at a people, then there is no reckoning for them."