Is it permissible for a worshiper to raise his head to the sky after straightening up from bowing?

It is not prescribed for the worshipper to raise his head towards the sky. Rather, his gaze should be directed towards the place of his prostration according to the majority of scholars, due to the humility it entails. Some scholars are of the opinion that it is preferable to look straight ahead. As for raising the head towards the sky after rising from bowing (ruku'), it is not prescribed, and whoever does it should be advised with gentleness and wisdom.