Luke 19:31

“And if any one ask you, ‘Why do you loose him?', thus shall you say, ‘The Lord has need of him.' ”

It may well be that He had already made an arrangement that He would collect it when He needed it and that whoever collected it would give a kind of password, ‘the Lord has need of him'. Or He may have been making use of the custom of ‘angaria' under which a major religious figure was entitled to procure for himself the use of a means of transport for a period of time by a simple act of appropriation. We are in fact probably intended to see in the use of the title ‘Lord' a deliberate indication that this was an unusual situation by which Jesus' supreme authority is being revealed. The whole arrangement thus indicates that Jesus has a special significance in what He is about to do. So it may well be that the ass's colt was offered for His free use as a major religious figure in accordance with the custom of angaria without previous arrangement.