A.T. Robertson Commentary John 19:34

"howbeit one of the soldiers with a spear pierced his side, and straightway there came out blood and water." — John 19:34 (ASV)

With a spear (λογχη). Instrumental case of this old word, here only in the N.T.

Pierced his side (αυτου την πλευραν ενυξεν). First aorist active indicative of νυσσω, old word to pierce, here only in N.T., and πλευραν (side), another old word, occurs in N.T. only here and Joh 20:20,25,27.

Blood and water (αιμα κα υδωρ). Dr. W. Stroud (Physical Cause of the Death of Christ) argues that this fact proves that the spear pierced the left side of Jesus near the heart and that Jesus had died literally of a broken heart since blood was mixed with water.