assure - shimaru48 @ ウィキ

as-(…に対し)+sure(確実である, 確信している)　cf. sure, ensure, insurance

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Take it easy. I can assure you that everything will turn out fine.
気楽にいけよ。大丈夫、すべてうまくいくさ

I am assured of his innocence [that he is innocent].
私は彼が無実だと確信している(=I'm sure that…)

I (can) assure you (that) she will come here. =She will come here, I (can) assure you.
彼女はきっとここへ来ますよ

I can rest assured of his recovery [that he will recover].
彼が回復するのは間違いないよ