Ten times is the voice of God speaking "out of the midst of the fire" heard in Deuteronomy: viz., chaps. iv.12,15,33,36; v.4,22(19)  , 23(20), 24(21), 25(21), 26(23).
Here, in Rev. i.10, John hears "a great voice," and it is connected with fire, for the eyes of the speaker were "as a flame of fire" (ver.14) and his feet "as if they burned in a furnace" (ver.15).
In Deut. iv.12 (the first reference) the expression is associated with the giving of the Law, and the declaring of Jehovah's Covenant (iv.13).
The second is a command to "take heed" to the voice (iv.15), and keep from idolatry.
The third and fourth are connected with their turning to the Lord when scattered among the nations, seeking Him and finding Him in the "Tribulation;" and the being obedient to that voice in "the latter days" (iv.27-36). This tells us of the latter days in Revelation, when they will be brought to hear the "Voice" (iv.33,36), and to attend to it.
The fifth is again associated with God's Covenant to which He will be true (v.4).
The sixth and seventh with the giving of the Law, v.22(19), 23(20).
The eighth with the greatness and the glory of Jehovah (v.24, Heb.21).
The ninth and tenth are references to it by the People (v.25,26).
All these are brought together, and combined, and fulfilled in the Apocalypse, when Israel will again hear that Voice and, take heed to it, and in their Tribulation turn unto the Lord and seek His face and find Him and rejoice in the faithfulness of a covenant-keeping God.
 The figures in a parenthesis denotes the different verse numeration of the Hebrew Text.