Strong’s Greek
G4469 — rhaka
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
ῥακά
rhaka — pronounced rhak-ah'
of Chaldee origin (compare 7386); O empty one, i.e. thou worthless (as a term of utter vilification):--Raca. see HEBREW for 07386
1 occurrence in the KJV.
Matthew 5:22
But I say unto you, That whosoever is angry with his brother without a cause shall be in danger of the judgment: and whosoever shall say to his brother, Raca, shall be in danger of the council: but whosoever shall say, Thou fool, shall be in danger of hell fire.