Or HaChaim on Numbers 28:3/אור החיים על במדבר כ״ח:ג׳

1-4. ואמרת להם זה האשה, "You shall say to them 'this is the fire-offering,' etc." G'd repeats once more: ואמרת. Why? The words זה האשה also do not seem called for. It appears the Torah wanted to make sure we would not think that the single sheep to be offered was a minimum only and that if the priests decided to, they could offer any number of sheep. The Torah therefore wrote "tell them only this is the fire-offering," i.e. only one sheep, neither more nor less. The same applied to the sheep to be offered in the evening. We must understand verse 3 as telling us that this sacrifice had to be offered on a daily basis. Verse 4 tells us that only the quantity specified by the Torah here and none other was acceptable for this type of sacrifice.