John 10:31

‘The Judaisers carried stones to stone him.'

Some of the Judaisers did recognise what He meant and were inflamed. To then this was blasphemy! Whatever their motives at the beginning they now lost control, for they went over to a nearby pile of rocks and picked up rocks, carrying them over in order to stone Him. This was not, however, the way in which He ought to die, so He sought to calm the atmosphere.

Stones would be available in the Temple area because building works were still in process. The verb suggests they went across to where these were going on and brought the stones back with them. Or it is even possible that they already carried them ready for this moment which they had precipitated.