What is the ruling on saying: "O angels of the night, awaken me for the night prayer or Fajr," or "O angels of the day, awaken me for any of the daytime prayers"?

There is no objection to saying: "O angels of God, protect me," if what is intended are the angels present with the servant day and night, such as the angels mentioned in the hadith: "Angels succeed one another among you by night and by day." This is not considered a prohibited form of seeking help (istighatha), because it is asking a living, present being for something within their capability, similar to asking parents or friends. This is permissible, as Allah Almighty says: "So the one who was of his party sought his help against the one who was of his enemy." Scholars have also mentioned that the thoughts of angels are always good.