Theophylact of Ohrid
Catena Aurea · Lukasevangelium 15
Either what woman having ten pieces of silver, if she lose one piece, doth not light a candle, and sweep the house, and seek diligently till she find it? And when she hath found it, she calleth her friends and her neighbours together, saying, Rejoice with me; for I have found the piece which I had lost. Likewise, I say unto you, there is joy in the presence of the angels of God over one sinner that repenteth.
Either they are friends as performing His will, but neighbours as being spiritual; or perhaps His friends are all the heavenly powers, but His neighbours those that come near to Him, as Thrones, Cherubims, and Seraphims.