A.T. Robertson Commentary Revelation 14:1

"And I saw, and behold, the Lamb standing on the mount Zion, and with him a hundred and forty and four thousand, having his name, and the name of his Father, written on their foreheads." — Revelation 14:1 (ASV)

The Lamb (το αρνιον). See 5:6; 7:17; 12:11; 13:8 and is in contrast with the anarthrous αρνιον in 13:11. This proleptic vision of the Lamb "standing on the mount Zion" (εστος επ το ορος Σιων, second perfect active participle neuter of ιστημ with επ and accusative) is reasoning after the visions of the two beasts. Mount Zion is the site of the new city of God (Hebrews 12:22), the Jerusalem above (Galatians 4:26), the seat of the Messianic Kingdom whether heaven or the new earth (Revelation 21; 22). These victors have the name of the Lamb and God upon their foreheads as in 3:12; 22:4, in place of the mark of the beast above (13:16; 14:11). This seal protects them (9:4).

A hundred and forty and four thousand (εκατον τεσσερακοντα τεσσαρες χιλιαδες). "Thousands" literally (χιλιας feminine word for a thousand and so εχουσα feminine plural). For the 144,000 see 7:5,8, though some scholars seek a distinction somehow.