The phrase is a "Salavat," a specific prayer used to honor and send blessings upon the Prophet Muhammad.
Allahumma Salli Ala Muhammadin Dua Meaning (Salwaat) - My Islam
Many practitioners find that repetitive recitation brings a sense of calm and removes anxiety. 4. Common Variations
A guide to (Salavat) involves understanding its meaning, its role in daily worship, and the spiritual benefits it brings to a Muslim's life. 1. Meaning and Translation
While the phrase you provided is a concise version, it is often extended:
"Allahümme salli ala seyyidina Muhammedin ve ala ali seyyidina Muhammed" (O Allah, bless our master Muhammad and the family of our master Muhammad).