I saw this gravestone in the Beheshte Zahra. It was the graves of two lovers who were married and they died together.
Asharafol Sadat Afzali (the bride) born in 1351 (1973) and died in 1371 (1993)
Asghar Shafiee (the groom) born in 1345 (1967) and died in 1371 (1993)

In Islam, Inna lillahi wa inna ilayhi raji'un is part of the Quran, Sura Al-Baqara, Verse 156. The full verse is as follows:

"Who, when a misfortune overtakes them, say: 'Surely we belong to Allah and to Him shall we return'."

Inna lillahi wa inna ilaihi raji'un

Sura Al-Baqara, Verse 156