Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) narrates from the Messenger of Allah (peace and blessings be upon him) that he said to him: Tell me of a deed which, if I do it, I will enter Paradise. He said: "Bakh bakh! You have asked about something great, and it is easy for the one for whom Allah makes it easy: establish the obligatory prayer, pay the obligatory zakah, and do not associate anything with Allah."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17258