Kneeled down (theis ta gonata). Second aorist active participle of tithēmi, placing the knees (on the ground). This idiom is not in the old Greek for kneeling, but Luke has it five times (Luk 22:41; Act 7:60; Act 9:40; Act 20:36; Act 21:5) and Mark once (Act 15:19). Jesus was standing at the right hand of God and Stephen knelt before him in worship and called on him in prayer.
Lay not this sin to their charge (mē stēsēis autois tautēn tēn hamartian). First aorist (ingressive) active subjunctive with mē, regular Greek idiom, Place not to them or against them (dative autois) this sin. The very spirit of Jesus towards his enemies as he died upon the Cross (Luk 23:34).
He fell asleep (ekoimēthē). First aorist passive indicative of koimaō, to put to sleep. Old verb and the metaphor of sleep for death is common in all languages, but it is peculiarly appropriate here as Jesus used it of Lazarus. See also Act 13:36; 1Co 15:18, etc. Our word cemetery (koimētērion) is the sleeping place of the dead. Knowling calls ekoimēthē here “a picture word of rest and calmness which stands in dramatic contrast to the rage and violence of the scene.”