swear
swear blind
warrant
demand
guarantee
swear down
ensure
lock into
buy
asseverate
if I'm lying, I'm dying
insist
maintain
attest
prove
carry conviction
adamancy
claim
overpromise
press home
avow
vow
yield
drive home
trust
ram home
affirm
convict
suppose
preach to the choir
pinky promise
aver
take
declare
oath
cross my heart and hope to die
win over
committed
truthen
fake the funk
verify
acknowledge
pass one's word
affirmative
believe
swear on a stack of Bibles
engage
admit
affirmation
flatter oneself
jump in with both feet
pill
true statement
probative
show
concede
establish
truth
mispromise
pledge
committedly
promising
assertorically
plight
a promise made is a promise kept
God's truth
trueness
put one's money where one's mouth is
depose
truthify
should
insistently
assertively
assertorily
good as one's word
promise
swan
assert
push
convincedly
vum
keep
sell
elocute
sell on
adamantean
assure