Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates that the Prophet (peace and blessings be upon him) said: "Usury (riba) has seventy doors, and shirk is likewise (that is, it too has seventy doors)."
Al-Bazzar recorded it, and its narrators are the narrators of the Sahih.
Ibn Majah recorded it in abridged form: "And shirk is likewise."
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب البيوع / 6572