Mus'ab bin Sa'd narrates from his father (Sa'd, may Allah be pleased with him) that he thought he had superiority over the other Companions of the Prophet (peace and blessings be upon him), so the Prophet (peace and blessings be upon him) said: "Indeed, Allah Almighty has helped this Ummah because of the supplication, prayer and sincerity of its weak people." Imam al-Bukhari (may Allah have mercy on him) recorded this hadith from the hadith of Muhammad bin Talhah, which he narrated from his father.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الاستسقاء / 6389