A.T. Robertson Commentary Hebrews 2:12

"saying, I will declare thy name unto my brethren, In the midst of the congregation will I sing thy praise." — Hebrews 2:12 (ASV)

Unto my brethren (τοις αδελφοις μου). To prove his point the writer quotes Ps 22:22 when the Messiah is presented as speaking "unto my brethren."

Congregation (εκκλησιας). The word came to mean the local church and also the general church or kingdom (Matthew 16:18; Hebrews 12:23). Here we have the picture of public worship and the Messiah sharing it with others as we know Jesus often did.