'Ministering' in the Bible

Are they not all ministering spirits, sent out for service on account of those who shall inherit salvation?

And Moses indeed was faithful in all his house, as a ministering servant, for a testimony of the things to be spoken after;

For God is not unrighteous to forget your work, and the love which ye have shewn to his name, having ministered to the saints, and still ministering.

And every priest stands daily ministering, and offering often the same sacrifices, which can never take away sins.