What is the evidence of Sheikh Ibn 'Uthaymeen for the rule that "everything that exits from the two private parts (or two natural orifices) invalidates ablution"?

The usual excretions from the two private parts (such as urine, feces, prostatic fluid, and wind) nullify ablution by scholarly consensus. As for rare excretions (such as worms, blood, stones, and hair), scholars have differed regarding them. The majority opinion is that they nullify ablution, while Malik held that they do not. The evidence for the majority is that these are excretions from the private parts and contain moisture, just as lochia (blood of postnatal bleeding) nullifies ablution, and it is also rare.