What is a "Sincerely Held Religious Belief?"

https://www.eeoc.gov/laws/guidance/section-12-religious-discrimination

https://www.callaborlaw.com/entry/defining-sincerely-held-religious-beliefs-that-might-excuse-mandatory-covid-19-vaccination

https://www.npr.org/2021/10/04/1042577608/religious-exemptions-against-the-covid-19-vaccine-are-complicated-to-get

https://www.employersgroup.com/covid-19/what-exactly-is-a-sincerely-held-religious-belief

https://ogletree.com/insights/what-is-a-sincere-religious-belief-the-fifth-circuit-weighs-in-on-a-religious-discrimination-claim/

https://news.utexas.edu/2017/06/09/what-are-sincerely-held-religious-beliefs/