Torah Temimah cites Yerushalmi Shevuos.
“A soul when it sins” — just as the oath of testimony incurs liability whether by formal oath or by imprecation (alah), so too the deposit-oath.
Hekesh of shevuah/alah — either formula triggers liability.
Any binding verbal denial formula can trigger the asham gezeilot structure. A formal oath and an imprecation are treated equivalently for this purpose.