Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) narrated: The Messenger of Allah (peace and blessings be upon him) said to me:
"The key to Paradise is testifying that there is no god but Allah."
Imam Ahmad and Imam al-Bazzar recorded it. In this narration there is a break (inqita') between Shahr and Sayyiduna Mu'adh (may Allah be pleased with him), and the narrations that the narrator Isma'il bin Ayyash transmits from the people of the Hijaz are da'if (weak), and this narration is one of them.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الإيمان / 10
Hadith Gradingمحدثین:إسناده ضعيف
Hadith Takhrij«اورده المؤلف فى زوائد المسند 12 ، أورده المؤلف فى كشف الاستار 2 كنز العمال ح 1825 . اخرجه السيوطي فى الدر المنثور 343/5»