What is the text of the hadith "There is no god but Allah is the key to Paradise"? And what are the teeth of the key to Paradise?

Some of this statement is marfū‘ (attributed to the Prophet) and some is mansūb (attributed to a Companion or Successor). The marfū‘ part is the hadith: "The key to Paradise is the testimony that there is no god but Allah," narrated by Al-Bazzar with a weak chain of transmission. It is attributed to Wahb ibn Munabbih, who said that "there is no god but Allah" is the key to Paradise, but every key has teeth, and if you come with a key that has teeth, it will be opened for you. Ibn Hajar holds the view that attributing this statement to the Prophet, peace and blessings be upon him, might be an interpolation by some narrators, inserting Wahb's words into the marfū‘ hadith.