In his first inspired sermon after receiving the Holy Spirit on Pentecost, the apostle Peter summed up God's instruction for mankind: "Repent therefore and be converted, that your sins may be blotted out, so that times of refreshing may come from the presence of the Lord, and that He may send Jesus Christ, who was preached to you before, whom heaven must receive until the times of restoration of all things, which God has spoken by the mouth of all His holy prophets since the world began" (Acts:3:19-21).

But what are these "times of refreshing" and "times of restoration" of which Peter spoke?

God's plan for mankind involves restoration. The Feast of Tabernacles symbolizes the restoration process, which will start with the return of Jesus Christ, pictured by the Feast of Trumpets, and the banishment of Satan, depicted by the Day of Atonement. Once these events have taken place, as represented by the previous Holy Days, the foundation is in place for the restoration of the creation to peace and harmony with God.
http://www.ucg.org/booklet/gods-holy-day-plan-promise-hope-all-mankind/feast-tabernacles-jesus-christ-reigns-over-all-e/

This year, in 2017, the Feast of Tabernacles (Sukkot) will begin in the evening of Wednesday, 4 October and ends in the evening of Wednesday, 11 October. This year's Feast of Tabernacles is very important.

The sons of God will be glorified towards the end of 2017. In order for this to happen, God must send the latter rain of His Holy Spirit. That is why this year's Feast of Tabernacle is special.

It was during a Feast of Tabernacles that Solomon’s Temple was dedicated to the Lord (1 Kings 8:2). It was also at the Feast of Tabernacles that the Israelites, who had returned to rebuild the temple, gathered together to hear Ezra proclaim the Word of God to them (Nehemiah 8 ). Ezra’s preaching resulted in a great revival as the Israelites confessed their sins and repented of them. (End time revival will begin during this year's Feast of Tabernacles.)
http://www.gotquestions.org/Feast-of-Tabernacles.html

During Sukkot (Feast of Tabernacles), two important ceremonies took place. The Hebrew people carried torches around the temple, illuminating bright candelabrum along the walls of the temple. Also, the priest would draw water from the pool of Siloam and carry it to the temple where it was poured into a silver basin beside the altar. The priest would call upon the Lord to provide heavenly water in the form of rain for their supply.

In the New Testament, Jesus attended the Feast of Tabernacles and spoke these amazing words on the last and greatest day of the Feast: "If anyone is thirsty, let him come to me and drink. Whoever believes in me, as the Scripture has said, streams of living water will flow from within him." (John 7:37-38 NIV) The next morning, while the torches were still burning Jesus said, "I am the light of the world. Whoever follows me will never walk in darkness, but will have the light of life." (John 8:12 NIV)
http://christianity.about.com/od/biblefeastsandholidays/p/feastofbooths.htm

Re. 7:2 Then I saw another angel coming up from the east, having the seal of the living God. He called out in a loud voice to the four angels who had been given power to harm the land and the sea:
Re. 7:3 “Do not harm the land or the sea or the trees until we put a seal on the foreheads of the servants of our God.”
Re. 7:4 Then I heard the number of those who were sealed: 144,000 from all the tribes of Israel.

Re. 14:1 Then I looked, and there before me was the Lamb, standing on Mount Zion, and with him 144,000 who had his name and his Father’s name written on their foreheads.
Re. 14:2 And I heard a sound from heaven like the roar of rushing waters and like a loud peal of thunder. The sound I heard was like that of harpists playing their harps.
Re. 14:3 And they sang a new song before the throne and before the four living creatures and the elders. No-one could learn the song except the 144,000 who had been redeemed from the earth.
Re. 14:4 These are those who did not defile themselves with women, for they kept themselves pure. They follow the Lamb wherever he goes. They were purchased from among men and offered as firstfruits to God and the Lamb.
Re. 14:5 No lie was found in their mouths; they are blameless.
Re. 14:6 Then I saw another angel flying in mid-air, and he had the eternal gospel to proclaim to those who live on the earth — to every nation, tribe, language and people.

Mt. 24:14 And this gospel of the kingdom will be preached in the whole world as a testimony to all nations, and then the end will come.

The 144,000 Israelites will arise during the Feast of Tabernacles. Notice that Rev 14:2 speaks about "the roar of rushing waters"--the latter rain; rivers of living water. Only Israelites who undergo the purification of Yom Kippur could be included among the 144,000. However, the necessary purification of Yom Kippur is not any of the ceremonies that Jews typically carry out during the Feast of Atonement; rather it is the washing by the blood of Jesus Christ.

Once the 144,000 Israelites arise, an angel will give them the eternal gospel, which is the end-time gospel of the kingdom, and they will preach it all over the world in a period of about forty days—quick short work. Then the resurrection or adoption of the sons of God will occur. This will later be followed by the rapture of the sons of God.