bear witness vs vouch

bear witness and vouch both are verbs.

Word	Noun	Adjective	Verb	Adverb
bear witness	No	No	Yes	No
vouch	No	No	Yes	No

As verbs, vouch is a hyponym of bear witness; that is, vouch is a word with a more specific, narrower meaning than bear witness:

bear witness (verb)	vouch (verb)
give testimony in a court of law	give supporting evidence
provide evidence for	summon (a vouchee) into court to warrant or defend a title
	give personal assurance; guarantee
	give surety or assume responsibility