John Gill Commentary Luke 24:8

"And they remembered his words," — Luke 24:8 (ASV)

And they remembered his words .
] That is, the words of Christ, as the Persic version expresses it; which they had forgotten, and it may be had never truly understood until now; and had now their memories refreshed with them by the angels, and their understandings opened by the Spirit of God.

Saints are sometimes apt to forget even the gracious promises of God, they have understood and received comfort from; the word, or words, on which they have been caused to hope, until the Spirit of God, who is their best remembrancer, puts them in mind of them.