There is nothing literal about the 144,000. Explained in detail here: http://144000.110mb.com/144000/index.html#II
The underlying symbolic components are numerous. First, Rev. 7:4-8 states that the 144,000 came from every tribe of the Israelites and then lists the names of what appear to be the original twelve tribes, but are not. As the Jehovah’s Witnesses point out, “there never was a tribe of Joseph, the tribes of Ephraim and Dan are not included in the list here, and the Levites were set aside for service in connection with the temple but were not reckoned as one of the twelve tribes. See Numbers 1:4-16” (Reasoning 166, 167). As such, the Jehovah’s Witnesses view the twelve tribes of the 144,000 symbolically.
Secondly, the sealed 144,000 listed are Jews, yet the Jehovah’s Witnesses regard this as symbolic as well for they believe they are comprised of both Jews and gentiles (Reasoning, 166, 167).
Third, whereas the listed 144,000 are made up of twelve distinct groups of twelve thousand members each, the Jehovah’s Witnesses also regard these numbers as symbolic. They have never classified or categorized those who go to heaven in twelve groups of 12,000 yet are quick to calculate them literally to arrive at 144,000 (12 x 12,000 = 144,000).
Fourth, the “seal on the foreheads of the servants” (Rev. 7:3), and the Lamb and His Father’s names which are written on the foreheads of the 144,000 (Rev. 14:1) represent figuratively, for the Jehovah’s Witnesses, God’s final approval. In their words, “God’s holy spirit serves as a seal that gives those sealed a token in advance of their inheritance, a heavenly one” (Insight, 253, 254). It is symbolic.
Fifth, Revelation 7:4 literally states that the 144,000 elect are virgin men: “These are the ones that did not defile themselves with women; in fact they are virgins.” But as anyone familiar with the Jehovah’s Witnesses knows, the 144,000 are comprised of men and women, married and single; they regard these provisions symbolically as well.
Sixth, additional evidence that the 144,000 number is not to be taken literally is found at Galatians 3:26-29 and Romans 9:6-8 where the apostle Paul makes clear that those who are rewarded with heaven due so in part as a consequence of God’s promise to the patriarch Abraham, and that the 144,000 heirs to the heavenly promise by virtue of faith are countless, without number, as numerous as the stars in the sky.
26 YOU are all, in fact, sons of God through YOUR faith in Christ Jesus. 27 For all of YOU who were baptized into Christ have put on Christ. 28 There is neither Jew nor Greek, there is neither slave nor freeman, there is neither male nor female; for YOU are all one [person] in union with Christ Jesus. 29 Moreover, if YOU belong to Christ, YOU are really Abraham’s seed, heirs with reference to a promise. (Galatians 3:26-29 NWT).
Abraham’s seed - descendant heirs according to the promise - are also identified at Romans 9:6-8 where Paul makes clear that the heirs to the heavenly promise are not limited to fleshly Israel.
6 However, it is not as though the word of God had failed. For not all who [spring] from Israel are really “Israel.” 7 Neither because they are Abraham’s seed are they all children, but: “What will be called ‘your seed’ will be through Isaac.” 8 That is, the children in the flesh are not really the children of God, but the children by the promise are counted as the seed. (Rom. 9:6-8 NWT).
Paul is referring to Genesis 15:5 where God promised Abraham that he would make his descendants like the stars of the sky, a promise that would eventually extend beyond fleshly Israel and encompass Christians.
5 He now brought him outside and said: “Look up, please, to the heavens and count the stars, if you are possibly able to count them.” And he went on to say to him: “So your seed will become.” (Gen. 15:5 NWT).
This Abrahamic promise was reaffirmed and recounted by Abraham’s grandson Jacob while praying to God for deliverance from his brother Esau.
“Unquestionably I shall deal well with you and will constitute your seed like the grains of sand of the sea which cannot be numbered for multitude.” (Gen. 32:12 NWT).
Given these verses it is difficult to imagine how the heirs to the heavenly promise number a mere 144,000. They do not. They will be countless, vast; large in actual numbers yet small in proportion to the billions who have ever inhabited earth. Never-the-less, the Jehovah’s Witnesses counter that those countless heaven-bound individuals are countless because they could not be counted at that time.
“God revealed the purpose and accomplishments of the Abrahamic covenant, saying that through Abraham the seed of promise would come; this seed would possess the gate of his enemies; Abraham’s seed through Isaac would number many, uncountable to man at that time.” (Insight, 522).
Well, I suppose they are correct in the sense that the heirs to the promise could not be counted so many thousands of years ago because they had not yet been born, and therefore there was nobody to count, but that’s not what the Almighty meant. Regardless of the ultimate count it seems evident that the heirs to the promise will eventually dwarf a mere 144,000. Even the Israelites who numbered in the millions were referred to as being as numerous as the stars (Deut. 1:10).
Seventh, that the 144,000 is not an exact number is made manifest by Jesus’ statement that the patriarchs Abraham, Isaac and Jacob will also be in heaven:
11 But I tell YOU that many from eastern parts and western parts will come and recline at the table with Abraham and Isaac and Jacob in the kingdom of the heavens; … (Matt. 8:11 NWT).
Central to the Jehovah’s Witnesses’ beliefs is the doctrine that the “Kingdom is in heaven, not earth” (NWT at 1653) and that neither the patriarchs, ancient prophets or anyone before the time of Christ goes to heaven. Yet somehow, in an effort to dislodge the patriarchs from heaven and disavow the words of Christ they theorize that this banquet in the kingdom of heaven is actually on earth.