Sayyiduna Abdullah bin Salam (may Allah be pleased with him) narrates: Once we were walking along with the Prophet (peace and blessings be upon him). He heard some people saying: "O Messenger of Allah! Which deed is most excellent?" The Prophet (peace and blessings be upon him) said: "Faith in Allah and His Messenger, jihad in the way of Allah, and an accepted Hajj (Hajj mabrur)." Then he heard a voice in the lower part of the valley; the man was saying: "I bear witness that there is no god but Allah Almighty, and that Sayyiduna Muhammad is the Messenger of Allah." The Prophet (peace and blessings be upon him) said: "I too bear witness to that, and I also bear witness that whoever bears witness to this (statement) will be free of polytheism (shirk)."
Ahmad recorded it, and al-Tabarani recorded it in al-Mu'jam al-Awsat; the narrators of both are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الجهاد / 9434
Hadith Gradingمحدثین:إسنادہ صحیح
Hadith Takhrij«اخرجه احمد فى المسند (451/5) ، أخرجه مسند أحمد برقم: 23271، وأخرجه الأحاديث المختارة برقم: 416»