476 - If a person takes an oath to one of the names of the word's of Allah such as God and Allah that he/she will perform an act, such as he/she will pray 2 Rak-at, it is obligatory to act this.
477 - If a person takes an oath that he/she will perform an act, but does not intentionally act according to his/her oath, he/she should give kaffarah for it, which means he/she should:
* Set a slave free
* fully feed ten indigent persons
* Provide ten indigents with clothes.
And if he/she is not able to perform these acts, he/she should fast for three conscutive days.
478 - If a person swears to confirm that he/she is telling the truth, and that is actually the truth, his/her taking of the oath is Makrooh, and if it is a lie taking of the oath is haraam and it is a major sin.