Sayyiduna Wathilah bin al-Asqa' (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said: "The greatest lie is that someone fabricates against me what I did not say, or makes his eyes see what they did not see, or ascribes himself to someone other than his father."
Hadith Referenceالمعجم الكبير للطبراني / باب الواو / 18394