In case of verbs having the sense of 'preventing, the desired object from which one is prevented or warded off', is called Ablation or apadāna kāraka,
The obstruction to one's natural inclination is called varana or prevention. As यवेभ्यो गां वारयति or निवर्तयति he wards off or withholds the cow from the barley.
Why do we say 'the object desired' is put in the ablative case' ? Observe गां वारयति क्षेत्रे he wards off the cow in the field.,