Acts 8:7

8:7 For unclean spirits, ¹  crying with loud shrieks, were coming out of many who were possessed, ²  and many paralyzed and lame people were healed.

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; ³ 

[8:7]  ¹ sn The expression unclean spirits refers to evil supernatural spirits which were ceremonially unclean, and which caused the persons possessed by them to be ceremonially unclean.

[8:7]  ² tn Grk “For [in the case of] many who had unclean spirits, they were coming out, crying in a loud voice.”

[16:17]  ³ 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.