Bricks should be soaked in water before using it in any brick work. Soaking of bricks has the following advantages.
Wetting of bricks removes any dirt, sand and dust from them.
Soaked bricks prevents suction of water from the wet mortar. If dry bricks are used then it will absorb water from mortar and mortar will become dry and cannot attain any strength.
Remember that bricks should be soaked in water for such a time period so that the water penetrates the whole depth of the brick. However bricks should not be soaked for a long period of time, as over wet bricks have following disadvantages.
There will not be proper adhesion between mortar and brick.
Brick may slip over the mortar creating difficulty in ensuring plumbness of the wall.
After soaking operation, bricks should be stacked on a clean place. Brick should be removed from the water sufficiently early so that at the time of laying they are skin dry.