'Sharp' in the Bible

Then Zipporah took a sharp stone, and cutting off the skin of her son's private parts, and touching his feet with it, she said, Truly you are a husband of blood to me.

Then his master is to take him to the gods of the house, and at the door, or at its framework, he is to make a hole in his ear with a sharp-pointed instrument; and he will be his servant for ever.