How do you say Rest in peace in Samoan?

Ia Manuia Lou Malaga

The literal translation of "Rest in peace" is "Malolo (Rest) i le filemu" or "Mapu (Rest) i le filemu" or "Moe (sleep/rest) i le filemu". These are lovely phrases. "Manuia lau (not lou) malaga" translates to "You have a blessed trip", or translating the idea/meaning, instead of "blessed", use "safe".