The phrase "undying devotion" refers to an enduring and unwavering devotion or loyalty towards someone or something that will never fade or diminish. Full definition
This is particularly true around Valentine's Day, when we're expected to open our wallets wide and passionately profess undying devotion to our beloved. (entrepreneur.com)
Kenney called for an emergency session of the Legislature, which under the current circumstances would be not much more than four pro-pipeline parties professing their undying devotion and love for the oil pipeline to Burnaby (just in time for Valentine's Day). (daveberta.ca)
All the Palestinians need to do is proclaim their undying devotion to Jesus. (religion.blogs.cnn.com)