Mark 16:17

16:17 These signs will accompany those who believe: In my name they will drive out demons; they will speak in new languages; ¹ 

Mark 16:20

16:20 They went out and proclaimed everywhere, while the Lord worked with them and confirmed the word through the accompanying signs.]]

[16:17]  ¹ tn Grk “tongues,” though the word is used figuratively (perhaps as a metonymy of cause for effect). To “speak in tongues” meant to “speak in a foreign language,” though one that was new to the one speaking it and therefore due to supernatural causes. For a discussion concerning whether such was a human language, heavenly language, or merely ecstatic utterance, see BDAG 201-2 s.v. γλῶσσα 2, 3; BDAG 399 s.v. ἕτερος 2; L&N 33.2-4; ExSyn 698; C. M. Robeck Jr., “Tongues,” DPL, 939-43.