Purity: Performance and Intention of Salat al‑Mayyit
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 592:
Salat al‑mayyit must be performed while standing and with the intention of attaining proximity to Allah. At the time of making the intention, the corpse must be specified; for example, one may make the intention: ‘I am performing the prayer for this corpse qurbatan ilal lāh (to attain proximity to Allah)’. And the obligatory precaution is that the type of stillness of body required in the daily prayers must be observed [in this prayer as well].
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)