Mukhtasar Bukhari

It is narrated from Sayyiduna Jundub (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever does a good deed to show off to the creation, Allah will make his bad intention known to everyone (on the Day of Resurrection), and whoever does a good deed to be seen by people, Allah will also show his true reality to everyone on the Day of Resurrection." (And they will not receive any reward.)