It is narrated from Sayyiduna Salman al-Farisi (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Indeed, Allah, the Blessed and Exalted, is modest and generous. When a servant spreads his hands before Him, He feels shy to turn them back empty."
Ja'far bin Maymun narrated this hadith in this way as marfu' (attributed to the Prophet), and Sulayman al-Taymi, in one of the two narrations from him, narrated it from Abu Uthman as mawquf (stopping at the Companion). This hadith is about supplication in general. A large number of the Companions raised their hands in the qunut, and in addition to that we have the hadith of Sayyiduna Anas bin Malik (may Allah be pleased with him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3146