I protect wooden handles on garden tools and knives, with mineral oil. I know it won't turn rancid ever. I apply mineral oil several times per year to protect tool handles against getting wet.

For handles where I want a very no-slip-grip, I wait for the mineral oil to sink in, and then rub a little beeswax on the handle. Parafin is cheaper, but beeswax is always a little "tacky" whereas parafin can be slick if I use too much.