Bhagavad Gita, Chapter 18, Verse 65

Occupy your mind with Me, be devoted to Me, sacrifice to Me, bow down to Me. You shall reach Myself; truly do I promise unto you, for you are dear to Me.

A direct promise, not a conditional hope: devote yourself to Krishna and you will reach him.

Krishna doesn't hedge this with qualifiers, he calls it his pledge outright. The certainty matches the closeness he has just described in the verse before it.