The Short Version
The global medical consensus strongly supports this claim for routine care of healthy infants. The WHO, AAP, and multiple independent clinical sources confirm that water poses real physiological risks — including hyponatremia, water intoxication, and nutritional displacement — and is unnecessary when infants receive adequate breast milk or formula. The only caveat is that the claim's absolute framing omits a narrow exception: water may be medically indicated in specific clinical scenarios such as severe dehydration, administered under professional supervision.