'Seventy' in the Bible

And Ahab had seventy sons in Samaria. And Jehu wrote letters, and sent to Samaria, unto the rulers of Jezreel, to the elders, and to them that brought up Ahab's children, saying,

Then he wrote a letter the second time to them, saying, If ye be mine, and if ye will hearken unto my voice, take ye the heads of the men your master's sons, and come to me to Jezreel by to morrow this time. Now the king's sons, being seventy persons, were with the great men of the city, which brought them up.

And it came to pass, when the letter came to them, that they took the king's sons, and slew seventy persons, and put their heads in baskets, and sent him them to Jezreel.