Sforno on Exodus 6:7/ספורנו על שמות ו׳:ז׳

1ולקחתי אתכם לי לעם, this will occur at the revelation at Mount Sinai.

2וידעתם, then the Israelites will realise that all of G’d’s promises have indeed come true. We find a similar verse in Deuteronomy 11,2 וידעתם היום כי לא את בניכם אשר לא ידעו, “you will know this day, that not with your children who did not know, etc.” but

3כי אני ה' אלוקיכם המוציא, that inasmuch as it is I, the Lord your G’d Who leads you out and watches over you very closely, AM THE ONE who will do everything that I promised.