This seventh holy day is observed immediately following the Feast of Tabernacles. Biblically, seven symbolizes perfection. It is also the eighth day of the Feast, and the Hebrew word for "eight" is related to another meaning "fatness," implying abundance, fertility - even resurrection and regeneration. According to Jewish tradition, on the Last Great Day, they finished reading what they started when Tabernacles began. Though intimately connected to the Feast of Tabernacles, it holds a distinct meaning of its own. It is part of it yet separate.
The offerings required on this day in the Old Testament were the largest of all, typifying Israel's thankfulness to God for all He provided. Today, God's people keep this day with praise and thankfulness - spiritual sacrifices (Hebrews 13:15) - for His abundant spiritual gifts.
Martin G. Collins
Holy Days: Last Great Day
The holy days and their offerings are shadows of good things to come (Hebrews 10:1). The offerings especially are indicative of many aspects of Christ's conduct and attitudes while serving God. We are to imitate Him (I John 2:6). Understood correctly, they represent the spiritual manner in which we are to observe these days.
Numbers 28:16—29:40 lists all the offerings to be made at the feasts. One can quickly see that more offerings were required for the Feast of Tabernacles than all other festivals combined. This ought to indicate what God expects regarding our conduct during the Feast of Tabernacles. He requires that we offer ourselves as living sacrifices so that it be most fruitful spiritually. It should be both a spiritual and physical feast whose fruit is rejoicing and learning to fear God as a result of the sacrifices done with understanding and a good attitude. This cannot be forced. It is the fruit of a right approach and use.
John W. Ritenbaugh
Amos 5 and the Feast of Tabernacles
Other Forerunner Commentary entries containing Leviticus 23:35:
1 Kings 12:28-33