The statistical distribution of temperature fluctuations in the cosmic microwave background is well understood as a nearly Gaussian field, making this a baseline definitional property of standard cosmology requiring no citation.
The claim states that the Gaussianity of the CMB describes the statistical distribution of its temperature fluctuations, which is a fundamental definition and everyday fact within observational cosmology. Per STEP 0, trivially true descriptive statements do not require citation and are classified as COMMON_KNOWLEDGE.