Then arose Ezra
 From the ground where he lay: 
 and made the chief priests, and the Levites, and all Israel, to swear
 that they should do according to this word:
 he took an oath of all that were present to do what was proposed, namely, to put away strange wives and their children: 
 and they sware;
 by means of which they were kept to their word of promise, an oath being a solemn, sacred, thing.