It is better to recite this dua in giving condolence

أَعْظَمَ اللَّهُ أَجْرَكَ، وَأَحْسَنَ عَزَاءَكَ، وَغَفَرَ لِمَيِّتِكَ

A'dhamAllahu 'ajraka, wa 'ahsana 'azaa'aka wa ghafara limayyitik.

May Allah increase your reward, grant you the tawfiq of patience (in mourning), and forgive the dead person.

Reference: Al-Adhkaar lin Nawawi P. 126