Reference for Chullin 161:24

קדשים בחוץ שני בלא תעשה

and according to R'Simeon, both incur the penalty of Kareth.<span class="x" onmousemove="('comment',' Since the slaughtering of the first animal was no slaughtering the second was fit to be offered this day in the Sanctuary, accordingly the penalty of Kareth is incurred even in respect of the second animal.');">⁹</span>

Jastrow

Jastrow