23 May 1634,
The leaders of the salt rebellion were arrested in Bilbao. That night they also banned leaving home under the threat of the death penalty. Three years earlier, on January 3, 1631, the royal decree entered into force in Spain, which increased the price of salt by 44%. In addition, the monarchy appropriated the monopoly of salt and ordered the Biscayan people to provide all the salt they had stored. Salt was a basic raw material for preserving food in denbo, and the Fueros de Bizkaia guaranteed the right to trade freely with salt and other products. Many citizens took arms and rebelled. The leaders of the rebellion were executed, except three who managed to escape.
Source:
Xosé Estévez, Las matxinadas en Euskal Herria (S. XVI-XIX) (Nabarralde).