اللَّهُمَّ بَارِكْ لَهُمْ فِيمَا رَزَقْتَهُمْ، وَاغْفِرْ لَهُمْ وَارْحَمْهُمْ
Allahumma barik lahum fima razaqtahum, waghfir lahum warhamhum
O Allah, segne sie in dem, was Du ihnen gegeben hast, vergib ihnen und erbarme Dich ihrer.
Dua for the host when being a guest
Making dua for those who host you is from the sunnah.