1754/1 - Anas ibn Mālik (may Allah be pleased with him) reported that the Messenger of Allah (may Allah’s peace and blessings be upon him) said: “How is it that some people raise their eyes towards the sky during prayer?” He stressed this point and added: “They must refrain from this or their sights will certainly be snatched away.” [Narrated by Al-Bukhāri]
1) It clearly informs that it is prohibited to raise one’s gaze towards the sky during prayer and points to the Prophet’s warning that those who act like this will lose their sight.
2) When a praying person looks at the place of his prostration, this boosts his humility and focus and indicates his politeness towards the Almighty Lord.