Or HaChaim on Deuteronomy 11:2/אור החיים על דברים י״א:ב׳

1 וידעתם היום, "and you shall know as of this day, etc." Moses means as of this day after you have reviewed all the proofs it is your duty to know that G'd has performed all these miracles as He did not perform them for your children. If your children who have only heard about all this would deny knowledge of these events this is one thing. You, however, who have witnessed all these events are in no position to deny knowledge of them. There was no need for Moses to define what precisely he meant by the word ידיעה, knowledge. They had seen with their own eyes miracles which proved that G'd is unique, has created the universe and is the supreme Ruler who despises those who disobey His laws and has chosen as His people those who adopt the laws of the Torah.