Jesus wanted his disciples to have total trust in him and the message they would preached.

The motivation used by Jesus to focus his disciples, was carried out in two ways.

a) that 'He' would take care of their physical needs and they should not concern themselves with any physical requirements. 

b) and Jesus also said that, the message they would preach, at each place, was so important that any city which would not receive them and hear the message, would be worse off than Sodom and Gomorrah.

Disbelief is not believing the message we are given, because we do not believe the messager.

It is common to pigeon-hole people because of our casual knowledge of them.

The essential message of Jesus could not believed by his own townspeople, because they believed Jesus was just like them. It was not possible for them to determine how Jesus had got his information irrespective of how impressive was that message.