أَعْلَى اللَّهُ دَرَجَتَهُ فِي دَارِ السَّلَامِ
May Allah raise his rank in the Abode of Peace.
Dār al-Salām is a designation of Paradise. Dār denotes an abode and salām conveys peace and safety. This is a prayer for the deceased scholar, not an assertion that he was promoted to a particular worldly office or city.
Contrast of functions:
'May Allah raise his rank' — a supplication.
'He died in Samarkand' — a historical statement.
Both can occur in one biography, but they perform different linguistic tasks. Recognizing the difference improves the reading of classical Arabic prose.