Can undead take Sarishan oaths?

Cool! I was going through my old stuff and remembered having this discussion a long, long time ago and never getting a proper answer

I would think a Sarishian Oath would end at death.

depends on how the contract is worded.

No one official, but I have stories.

In the 3.5 days there was a module where the players had to help the dead Patriarch of the Coryani Mother Church (Elandra’s position in current game year)
He had sworn by Sarishian Oath to the women that he loved in his 20’s that he would return a holy symbol she had given him before he went off adventuring. He never ended up with her, and kept the symbol intending to return it later.
When he died as an old man, the symbol was not returned to her, and his soul was barred from the typical afterlife (Cauldron or Paradise) and we was a shade in torment.
If the players failed to return it, then his torment continued without end.

Also there was a cup, Chalice actually that was blessed by Beltinians, and Sarishians, that enacted a very special Oath between two people. It allowed a person could enter the Paradise of the Gods upon death, in exchange the other person was forced to serve as a General in armies of Sarish instead of going to Paradise, or going to the Cauldron.

I would say yes, Sarishian Oaths carry on into death, and can in fact affect your afterlife.
A common person might say “I swear by Sarish…” but only a fool enters into one of His contracts without being careful with the wording.