Acting on those voices Henare entered the bank about 10.40am carrying a backpack with a large knife hidden inside.
He handed his bank card to a teller and asked for his account balance then left but hung around outside for about 15 minutes before entering the bank again with the knife.
Henare then brandished the knife at bank staff and customers, then climbed over a glass petition and ordered one teller to hand over cash.
He told two other tellers to do the same then ran away, but was located by police soon after. Inside his backpack were the bankcard, the knife and stolen cash.
Judge Paul Mabey QC said he had a number of medical reports on Henare and was satisfied he did not have an insanity defence at the time of the robbery.
But Judge Mabey said it was clear Henare's actions were in part driven by his illness which reduced his "moral culpability".
Henare's lack of prior convictions, previous good character, his age and remorse were also taken into account in the three years and seven months prison sentence he imposed, he said.
Judge Mabey also ordered Henare to be retained as a special patient in the hospital subject to a compulsory treatment order under the Mental Health Act.
This means Henare cannot leave unless granted release.