Al-Walid bin Malik (may Allah be pleased with him) states: A man entered the mosque and began to pray. The Prophet (peace and blessings be upon him) said: "Will someone give charity to this man by praying with him?" The narrator states: So a man stood up and prayed with him, and the Prophet (peace and blessings be upon him) said: "These two are a congregation."
Imam Ahmad recorded this narration. The narrator named al-Walid is not a Companion, and this hadith is munqati' (broken) in its chain.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2181