once
وَقَالَ صلى الله عليه وسلم:((إِنَّ لِلَّهِ مَلاَئِكَةً سَيَّاحِينَ فِي الْأَرْضِ يُبَلِّغُونِي مِنْ أُمَّتِي السَّلاَمَ)).
Meaning
The Prophet [PBUH] said:'Indeed Allah has angels who roam the earth and they convey to me the greetings (or prayers of peace) of my 'Ummah (nation).
Source and references
Hisn al-Muslim, entry 222.The reference is copied from the edition; separate editorial verification is not complete yet.
Source edition: Fortress of the Muslim. Open source ↗