Sunan Ibn Majah, Chapter: The Chapters on Etiquette

the Messenger of Allah (saw) passed by him when he was planting a plant, and said: "O Abu Hurairah, what are you planting?" I said: "A plant for me." He said: "Shall I not tell you of a plant that is better than this?" He said: "Of course, O Messenger of Allah." He said: "Say: 'Subhan-Allah, wal-hamdu-lillah, wa la ilaha illallah, wa Allahu Akbar (Glory is to Allah, praise is to Allah, none has the right to be worshiped but Allah and Allah is the Most Great.)' For each one a tree will be planted for you in Paradise."