Acts 20:36 (WEB)
When he had spoken these things, he knelt down and prayed with them all.
Catechism · 1
“The first Christian communities lived this form of fellowship intensely.” — Catechism footnote: Cf. Acts 12:5; 20:36; 21:5; 2 Cor 9:14.
Fathers and councils · 1
“All the churches did not, however, adopt this practice; for we see in the Acts of the Apostles (xx. 36 and xxi. 5) that St. Paul prayed kneeling during the time between Pentecost and Easter.” — the author cites it
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Cross-references · 1
Cited together in First Council of Nicaea, Canon 20.