Answer:

VOW

Answer	Crossword Clue
VOW	"I do," e.g.
VOW	Declare
VOW	Formal promise

VOW	Oath
VOW	Promise
VOW	Swear
VOW	Pledge
VOW	"I ... to Thee, My Country" (Anglican hymn)
VOW	Formal pledge
VOW	Monastic pledge
VOW	Solemn promise

VOW	One taken in marriage
VOW	Assurance
VOW	Altar pledge
VOW	It may be solemn
VOW	Altar assurance
VOW	Altar agreement
VOW	Give one's word
VOW	Altared statement?

VOW	Nonvulgar swearing
VOW	Sworn statement
VOW	"I shall return," e.g.
VOW	Exchanged words
VOW	Resolution
VOW	Formal declaration
VOW	Say "I do"
VOW	Resolve

VOW	Solemn commitment
VOW	Sacred oath
VOW	"Cross my heart," e.g.
VOW	One given at a wedding
VOW	Sacred assurance
VOW	Take an oath
VOW	Solemn pledge
VOW	Assert emphatically

VOW	Altar declaration
VOW	"I do," for one
VOW	Commitment
VOW	Solemn oath
VOW	Personal commitment