Sayyiduna Ka'b bin Malik (may Allah be pleased with him) said to the Prophet (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 are showering them with arrows."
Hadith Referenceالمعجم الكبير للطبراني / باب الكاف / 16201