Rev 14:1-5

THE 144,000
Here, in Chapter 14, we again meet the 144,000, where they remove the lawlessness from the kingdom of heaven. At the end of the Chapter, the Rider on the White Horse tramples the lawlessness from Christ’s kingdom, “the great winepress” that is described in Rev 19:15, and Rev 14:20. This is the work of the 144,000 described in verses 1-5.

The Rider on the White Horse, and the 144,000, are two different descriptions of the Sanctified Church of the end days.

In Chapter 7, we saw that the “144,000” as the twelve tribes of “New Jerusalem” described in Ezek 48; the City called “THE LORD IS THERE,” (Ezek 48:35). This is the “New Jerusalem,” that has the presence of the spirit of God, the spirit of truth. In Chapter 7, the 144,000 were “sealed by the holy spirit,” (Rev 7:3, Eph 1:13).

The 144,000 are “the bond-servants of God” (Rev 7:3), all the elect of God, who do His work in the last days.

In Rom 11:25, Paul said: “a partial hardening has happened to Israel until the fullness of the Gentiles has come in.” The close relationship between Israel, and the end time sanctified Church is emphasized by “the 144,000.”
1 I saw, and behold, the Lamb standing on Mount Zion, and with him one hundred forty-four thousand, having his name, and the name of his Father, written on their foreheads. 
Rev 14:1
the Lamb standing on Mount Zion – Mount Zion represents the Sanctified Church, the Mountain that was first described in Isa 2:2. The Lamb “on Mount Zion” speaks of the washing of the Church by the blood of the Lamb. This is the Holy and Sanctified Church of the end days.

His name on their foreheads – this is the name of Jesus, the name of the body of Christ,  the name of the temple of God, the sanctified Church, as described in Rev 3:12, see additional commentary there.
2 I heard a sound from heaven, like the sound of many waters, and like the sound of a great thunder. The sound which I heard was like that of harpers playing on their harps. 
Rev 14:2
a voice from heaven – this is “heaven” as described in Rev 12:1, Rev 12:12, and Rev 13:6. These are the saints of New Jerusalem.

like the sound of many waters – this is the sound of end-time Sanctified Church, that we see in Rev 19:6; and Ezek 43:2-7.

like the sound of thunder…like the sound of harpists – the sound of the holy spirit of God providing a diversity of tongues; the harps we see in Rev 15:2 – which Paul compares to speaking in tongues in 1 Cor 14:7, and the sound of thunder, that speaks “Hallelujah! in Rev 19:6.
3 They sing something like a new song before the throne, and before the four living creatures and the elders. None could learn the song except the one hundred forty-four thousand, those who had been redeemed out of the earth.
Rev 14:3
they sang a new song – they are like the those who bring out things old and new (Matt 13:52); the Israelites now sing the Song of the Lamb, as well as the Song of Moses, as described in Rev 15:3. They have become the chosen people of two covenants.

and no one could learn – this is a spiritual song, they are singing with the Spirit, it is the “the song of the lamb,”as described in 1 Cor 14:15.
4 These are those who were not defiled with women, for they are virgins. These are those who follow the Lamb wherever he goes. These were redeemed by Jesus from among men, the first fruits to God and to the Lamb.
Rev 14:4
not defiled by women – not defiled by the Great Harlot (Revelation Chapter 17), they are pure and do not accept corrupt doctrines.  The 144,000 are the Sanctified Church, the spotless bride of Christ.

They follow the Lamb wherever He goes – they only follow the teachings and example of Jesus Christ.

as first fruits to God – Jesus said: “the last will be first, and the first last” (Matt 20:16).  Israel as last, are also the firstfruits to God.
5 In their mouth was found no lie. They are without fault. 
Rev 14:5
no lie – they will only follow the truth.