The phrase "unchanging nature" refers to something that remains the same or consistent over time, without any significant alterations or modifications. Full definition
The hypothesis of a definitive halt in terrestrial evolution is, to my mind, suggested less by the apparently unchanging nature of present forms than by a certain general aspect of the world coinciding with this appearance of cessation. (religion-online.org)
Any behavior can be ascribed to this alleged unchanging nature when combined with the convenient explanation of mysterious ways, unknown plan, and the other horn of the dilemma, i.e. whatever the deity does is invariably good because it is the deity acting. (religion.blogs.cnn.com)
Your notion of a perfect unchanging nature is above and beyond your alleged deity's ability to choose, i.e. it is a source of morality apart from the free will agency of the deity. (religion.blogs.cnn.com)