Abd al-Rahman bin Ka'b bin Malik narrates from his father, Sayyiduna Ka'b bin Malik (may Allah be pleased with him), that he said to the Messenger of Allah (peace and blessings be upon him): Allah has revealed concerning poetry what He has revealed. He (peace and blessings be upon him) said: "The believer strives (in jihad) with his sword and his tongue. By the One in whose hand is my soul, it is as though you were showering them with arrows."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 21108