Full Idea
Upward Löwenheim-Skolem: every first-order theory with infinite models has arbitrarily large models.
Gist of Idea
Up Löwenheim-Skolem: if infinite models, then arbitrarily large models
Source
Wilfrid Hodges (First-Order Logic [2001], 1.10)
Book Reference
'Blackwell Guide to Philosophical Logic', ed/tr. Goble,Lou [Blackwell 2001], p.29