Malik narrates that he asked al-Sha'bi about the tashahhud, and he said that Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him), after "Peace be upon you, O Prophet, and the mercy of Allah", used to say: "Peace be upon us also from our Lord."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9152