It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "People must desist from raising their gaze towards the sky at the time of supplication in prayer, or their sight will be snatched away."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3537