Eternal good deeds are -

سُبْحَانَ اللَّهِ، وَالْحَمْدُ لِلَّهِ، وَلَا إِلَهَ إِلَّا اللَّهُ، وَاللَّهُ أَكْبَرُ، لَا حَوْلَ وَلَا قُوَّةَ إِلَّا بِاللَّهِ

SubhaanAllah, walhamdu lillaah, wa Laa 'ilaaha 'illAllah, wa Allahu 'Akbar, Laa hawla wa laa quwwata 'illaa billaah

How perfect Allah is, and all praise is for Allah. None has the right to be worshipped except Allah, and Allah is the greatest. There is no might nor power except with Allah.

Reference: Musnad-e Ahmad (no. 513) (Ahmad Shakir, ed.) and its chain of narration is authentic. See Majma'uz-Zawa'id 1/297. Ibn Hajar mentions it in Bulughul-Maram saying that Ibn Hibban and Al-Hakim considered it authentic.