Early 400sAD: 1 John 5:7 is in a Greek lectionary book named Apoftolos [Apostolos]-439AD

"8. This verfe [verse, 1 John 5:7] is also found in the Apoftolos [Apostolos] or Collection of Leffons [Lessons], read in the Greek Church, out of the Apoftolical Epiftles [Apostolical Epistles], and printed at Venice, An. 1602. Velut ab Antiquis feculis recepta Lectio, fays [says] Selden de Synedriis, l.2 c.4 Art 4. This Lectionary is as old as the fifth Century [5th Century=400sAD]. Vide Millii Prol. 1054 and Mr. Martin's Differtation [Disssertation], Part I [1]. c. 13.
(Bottom right picture from
A Critical Examination of the late New Text and Version of the New Testament,.../ by Leonard Twells, Page 129)

Pages 85 & 86 images, A critical dissertation upon the seventh verse of the fifth chapter of St. John's first epistle,...wherein the authentickness of this text is fully prov'd against the objections of Mr. Simon and the modern Arians. Written originally in French by Mr. Martin, and now translated into English. 1719