Sayyiduna Samurah bin Jundub (may Allah be pleased with him) narrates this saying of the Prophet (peace and blessings be upon him): "The most virtuous charity is that of the tongue." It was asked: "O Messenger of Allah, what is the charity of the tongue?" The Prophet (peace and blessings be upon him) said: "Intercession that frees a captive, or ends a matter of blood-retaliation, or through which you bring some good or kindness to your brother, or repel something hateful from him."
Al-Tabarani recorded it; its chain contains Abu Bakr al-Hudhali, who is da'if (weak).