The correct answer to this open question is the following.
Although the question is incomplete and has no references attached, we can say that it refers to the "Manchola letter," written by Tejan-Mexican Rafael Manchola in 1826.
The source of the letter is trustworthy as evidence of why Texans revolted because it was written by an individual that lived in the Texan territory in 1826. In the letter, Manchola wrote to a military official that the American colonists could not be trusted because they did not follow rules. Just followed their own rules. Manchola noted that the American colonists that settled the Texan territory had promised to respect and followed the Mexican law.