Isaiah of Scetis is not listed in the UBS4 list of patristic witnesses, and very little attention, it seems, has been given to him.
Isaiah of Scetis ("Scetis" = the Place of the Ascetics, in the Natron desert (in Egypt)) was a monastery-leader in Egypt in the mid/late 400's. He utilized Scripture incessantly in the work "Ascetic Discourses." His mind seems to have been brimming with the Word so much that it very frequently spilled into his spontaneous thoughts.
Alin Suciu has some information at his blog about Isaiah of Scetis (just search there for "Isaiah of Scetis"), as well as links to various related resources. One resource that he mentions is particularly valuable: "Abba Isaiah of Scetis: Ascetic Discourses," translated into English by John Chryssavgis and P. R. Penkett. Chryssavgis/Penkett provide a nice English rendering of Isaiah of Scetis' Ascetic Discourses (a.k.a. Asceticon), with footnotes wherever Scripture is utilized.
Isaiah of Scetis occasionally quoted chunks of Scripture; for example in Discourse 21 (On Repentance), he presents a few whole verses from First John, followed by whole verses from John 17, followed by whole verses from Luke 6 and John 15, followed by a quotation of Matthew 19:27-29, followed by a quotation of verses from First John, followed by whole verses from Second Peter, followed by whole verses from Ephesians, followed by several verses from First Corinthians, and these are just a sample; there are also quotations from Mt., Mk., Acts, Revelation, etc. And that's just one discourse!
Some other features of the Ascetic Discourses of Isaiah of Scetis (these are just samples!):
Discourse 4 features a quotation of Mt. 5:25-26.
Discourse 7 features a quotation of Ephesians 6:11-13.
Discourse 8 features a quotation/use of Luke 23:42 (with "Lord") (This is misidentified in the footnote as 22:42).
Discourse 11 begins with a quotation of Mt. 13:31.
Discourse 13 includes quotations from Mt. 11:4-6 (or is it Luke 7:22-23?), Philippians 3:10-11, Hebrews 10:34, Mark 15:34, Colossians 3:1-3, et al.
Discourse 15 features quotations of II Cor. 5:10, Philippians 3:21, and Romans 8:35.
Discourse 16 features quotations from Luke 21:34, Luke 10:18-19, Luke 12:32-33, Luke 22:28-30, Galatians 2:20, and an allusion to Rev. 3:10.
Discourse 18 begins with quotations from Philippians 4:5-7, Colossians 3:15, and a specific quotation ("In the Gospel of Mark, the Lord says to His disciples" --) from Mark 11:25 (listed as 11:26 in the footnote).
Discourse 19 features quotations from Luke 17:21, John 1:12-13, Ephesians 3:16-18, Colossians 3:15 (with "of Christ"), Luke 12:35-36, et al.
Discourse 22 features quotations from Colossians 2:11-12, Ephesians 4:22-24, First Peter 2:24b, and II Cor. 5:1 (not footnoted).
Discourse 23 features quotations from Luke 14:4, Luke 10:6, and Mt. 7:14 ("Straight is the gate and narrow is the way...").
Discourse 25 features quotations of I Cor. 11:7-12, Romans 7:2-3, First John 5:18, Hebrews 6:13-14, John 21:5, First John 2:12-13, Matthew 18:32-35, James 5:19-20, Mt. 7:13-16, Romans 8:38-39, Ephesians 5:30, John 14:15-17, and other passages.
Discourse 27 features quotations from Luke 17:10 and James 4:17.
Discourse 28 features a quotation of Mt. 7:22-23.
Yours in Christ,
James Snapp, Jr.