Or HaChaim on Exodus 25:3/אור החיים על שמות כ״ה:ג׳

1 וזאת התרומה, This is what the gift consists of, etc. The conjunctive letter ו which introduces the word זאת may indicate that the duty of contributing to the Tabernacle could not be discharged by the offering of only one or a few of the categories of building materials required. Unless all the materials specified were contributed directly, the Israelites had not fulfilled their duty. The letter ו then stipulates an additional directive, i.e. not only must you donate generously, but you must donate of all the thirteen materials required. The Tabernacle which represented a re-enactment of the work of creation could not be completed without the presence of all the ingredients listed. Alternatively, the meaning could be that all of the thirteen kinds of materials should be equally welcome. Someone who contributed flax (linen) or skins was not to be looked down upon when compared to someone who contributed gold, for instance.