This phrase is from the book of Daniel. His audience would have been familiar with this passage and the prophecy about the abomination entering the temple and defiling it. AT: "the shameful thing that defiles the things of God" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Jesus' audience would have known that this refers to the temple. This can be made explicit. AT: "standing in the temple, where it should not be standing" (See: [[rc://en/ta/man/translate/figs-explicit]])
This is not Jesus speaking. Matthew added this to get the readers' attention, so that they would listen to this warning. AT: "may everyone who is reading this pay attention to this warning" (See: [[rc://en/ta/man/translate/figs-explicit]])