assure

verb

1. make certain of"This nest egg will ensure a nice retirement for us"
2. inform positively and with certainty and confidence"I tell you that man is a crook!"
3. assure somebody of the truth of something with the intention of giving the listener confidence"I assured him that traveling to Cambodia was safe"
4. be careful or certain to do something; make certain of something"He verified that the valves were closed"
5. make a promise or commitment