This claim comes from a Bluesky post by user Max Granger, that has since been deleted. The initial post claimed that the Senate unanimously passed a Charlie Kirk remembrance day resolution. It further claimed that all democratic senators, specifically mentioning Bernie Sanders, voted yes.
A PDF, which contains a resolution submitted by Rick Scott
https://www.rickscott.senate.gov/services/files/55A19212-1EC1-4868-A72B-8E271E2D81B2
Rick Scott, a senator from Florida, submitted the following resolution to the Senate to officially declare October 14th as Charlie Kirk remembrance day. The main reason for the remembrance is that “ Charlie Kirk was a champion of free speech, civil dialogue, and faith.” The resolution provides many other reasons for which Kirk should be honored. This is a legitimate resolution that was submitted to the Senate.
An article on ABC News, written by Megan Forrestor
https://abcnews.go.com/US/senate-passes-national-day-remembrance-charlie-kirk/story?id=125730824
This article clarifies that the Senate and House did unanimously pass a national day of remembrance on October 14th to honor Charlie Kirk. The day was decided as it was his birthday. The resolution was unanimously approved in the Senate. The House also approved the resolution, however 96 democratic representatives and 4 republic representatives declined to support it. 22 democratic representatives walked out of the hearing without voting.
An outline of unanimous consent agreements in the senate
https://www.senate.gov/about/powers-procedures/rules-procedures/first-unanimous-consent-agreement.htm
This outline, states that unanimous consent agreements are agreements reached in the Senate in which no formal vote is held, but no present member objects to a proposed resolution.
https://www.sanders.senate.gov/press-releases/prepared-remarks-sanders-delivers-speech-on-his-intent-to-file-joint-resolutions-of-disapproval-to-block-20-billion-arms-sale-to-israel/
This article, outlines a speech given by Bernie Sanders to the Senate on September 18th, the day the resolution was passed, indicating he was present.
While Bernie Sanders did not object to the resolution, no formal vote was held, thus the claim that all democratic senators voted yes is false.