When Moses was given instructions about building the Tabernacle, he didn’t use exactly the same words in transmitting these instructions to the people. Why did he change the wording? In particular, why did he add “vavs” to the list of items that were used?
The specific question of the vavs is discussed in the Talmud (Avodah Zarah 23b-24a). The issue is whether donations for the Tabernacle (or Temple) can be accepted from non-Jews. The commandment to Moses about Terumah (donations) is addressed to “Benei Yisroel”, implying that only donations from Jews are acceptable. The Talmud proposes that some items can be accepted from non-Jews because those items are not linked to the commandment by vavs – for example, “avnei shoham” in Ex. 25:7. This proposal is withdrawn when it is pointed out that the missing vav is supplied in Ex. 35:9. The Talmud deals only with the vav attached to “avnei shoham”, but Tosafos R.Elchanan points out that the same is true for the vav attached to “shemen la-maor”, which is missing in 25:6 but supplied in 35:8. Thus Moses added the vavs to link all the items on the list to the original commandment, to teach us that donations of these items can only be accepted from Jews.