Catena Fidei

Acts 3:17 (WEB)
“Now, brothers, I know that you did this in ignorance, as did also your rulers.

Catechism · 3

§591Paragraph 1 · Jesus and IsraelRead at vatican.va
“The members of the Sanhedrin were thus acting at the same time out of "ignorance" and the "hardness" of their "unbelief".” — Catechism footnote: Cf. Lk 23 34; Acts 3: 17-18; Mk 3:5; Rom 11:25, 20.

§597Paragraph 2 · Jesus Died CrucifiedRead at vatican.va
“Jesus himself, in forgiving them on the cross, and Peter in following suit, both accept "the ignorance" of the Jews of Jerusalem and even of their leaders.” — Catechism footnote: Cf. Lk 23:34; Acts 3:17.
§600Paragraph 2 · Jesus Died CrucifiedRead at vatican.va
“For the sake of accomplishing his plan of salvation, God permitted the acts that flowed from their blindness.” — Catechism footnote: Cf. Mt 26:54; Jn 18:36; 19:11; Acts 3:17-18.

John Chrysostom, Homilies on John Homily 83
“For He sent the Apostles also for their salvation, at least thou hearest them saying, that, “We know that through ignorance ye did it” ( Acts iii. 17 ); and by these means drawing them to repentance.” — the author cites it
Read the whole comment

Clement of Alexandria, The Stromata, or Miscellanies VI.6Book VI
“But to all rational souls it was said from above, “Whatever one of you has done in ignorance, without clearly knowing God, if, on becoming conscious, he repent, all his sins will be forgiven him.”” — editor's note: Alluding apparently to such passages as Acts iii. 17, 19, and xvii. 30.
Read the whole comment