Strong's G4828 — συμμαρτυρέω (verb)
summartureo (soom-mar-too-reh'-o) v.
1. to testify jointly, i.e. corroborate by (concurrent) evidence
[from G4862 and G3140]
KJV: testify unto, (also) bear witness (with) 
Root(s): G4862, G3140 
Hebrew root: μαρτυρέω
Occurrences: 3