neverni Toma

1. humor. a doubting Thomas
   Ne budi neverni Toma, videćeš da je istina. — Don't be a doubting Thomas, you'll see it's true.
   Moj brat je pravi neverni Toma, ništa ne veruje dok ne vidi. — My brother is a real doubting Thomas; he believes nothing until he sees it.

Usually teasing or mildly reproachful. Also said of women, without changing the form.