Our Gemara on Amud Beis notes that most gosessim (those imminently dying) do not recover. This sparks debate in poskim: If someone was a goses before Shabbos, can one pray for them on Shabbos, or should one assume they’ve passed, avoiding a prayer that disrupts Shabbos tranquility (Aruch Hashulchan, OC 288:16)? Some argue against praying even during the week without verifying their status, as praying for the impossible (e.g., a deceased person’s recovery) is forbidden (Shulchan Aruch, OC 230:1). Nachalas Shiva (39 and 88) permits prayer, as the person might be alive, and the intent to ease suffering justifies it, even if the person’s status is unknown.

Modern sensibilities struggle with the idea that prayer can disrupting Shabbos or of it being “wasted” because most people don’t feel such a sanctity of Shabbos or an intensity of prayer that they’d be concerned about something being disrupted or wasted. But the law is the law. 

An interesting question arises related to the concept of the wasted prayer. The Ribon Kol Olamim prayer, recited Friday night, states: “I give thanks before You…for all the kindness that You have done for me and that You will do for me.” Thanking God for future acts seems presumptuous, akin to a wasted prayer. I am not aware of any such prayer aside from this. Perhaps the answer is that On Shabbos, we must feel all work is complete (Shulchan Aruch, OC 306:8). The prayer’s author embraces this mindset, thanking God for future blessings as if assured, reflecting deep trust in divine providence and Oneg Shabbos.