Vows (5)
'vows' is the definition.
('oath' can be a synonym of 'vow')
This is all the clue.
(Other definitions for oaths that I've seen before include "truths may be established by them" , "Solemn vows" , "Solemn sworn promises" , "four-letter words" , "Curses - words of honour?" .)
(Other definitions for promises that I've seen before include "Undertakings, vows" , "''But I have ...to keep / And miles to go before I sleep'' (Robert Frost)" , "Makes a commitment" , "Commitments, vows" , "Pledges (often repeated!)" .)