What is the appropriate response to the saying "Al-Baqa Lillah" (Survival/Continuity belongs to Allah) during condolences, and is responding with "Subhan man lahu al-baqa' wal-dawam" (Glory be to Him to whom belongs survival and perpetuity) permissible?

Expressions of condolence are not limited to specific phrases; rather, any phrase with a sound meaning is permissible, including the saying: "Survival/Everlastingness belongs to Allah" (البقاء لله); for survival is one of Allah's inherent attributes, and "the Everlasting" (الباقي) is one of Allah's Beautiful Names. It is also permissible to say: "Glorified is the One to whom belongs survival and perpetuity" (سبحان من له البقاء والدوام). As for responding to the one offering condolences with the phrase: "Survival/Everlastingness belongs to Allah" (البقاء لله), the response should be by reciting the verse: "Indeed, to Allah we belong and to Him we shall return" (إنا لله وإنا إليه راجعون).