Rashi on Exodus 30:31/רש"י על שמות ל׳:ל״א

1לדרתיכם THROUGHOUT YOUR GENERATIONS — From here our Rabbis derived that it (the oil of anointment) was miraculously preserved in its entirety for the time to come (for the Messianic days) (Horayot 11b).

2זה has the numerical value of 12, alluding to the 12 “logs” which was the measure for the oil of anointment (Horayot 11b; cf. Rashi v. 24).