Short answer
– From a mainstream evangelical standpoint the most likely author of 1 John (and therefore of 1 John 5:14–15) is the Apostle John — the “beloved disciple,” an eyewitness of Jesus and a leader in the early Ephesian church. Evangelicals treat the epistle as inspired Scripture, written to give pastoral teaching and assurance to believers.

Who John is (traditional evangelical summary)
– John son of Zebedee, brother of James: a Galilean fisherman called by Jesus (Matt. 4:21–22; Mark 1:19–20).
– Member of Jesus’ inner circle (with Peter and James): present at the Transfiguration and at Gethsemane.
– Traditionally associated with Ephesus/Asia Minor in his later years and with the Gospel of John, the three epistles, and (by many) Revelation.
– Referred to in the Gospel as “the disciple whom Jesus loved,” and in 1 John the author speaks with eyewitness authority (“that which we have heard, which we have seen…” 1 John 1:1–3).

Evidence supporting Johannine authorship
– Internal: the epistle claims firsthand testimony (“we have heard… seen… handled,” 1 John 1:1–3) and uses distinct Johannine themes and vocabulary (light/darkness, love, truth, Son of God).
– External: early church tradition (e.g., Irenaeus and other Fathers) attributes the letters to John the Apostle. Evangelicals typically accept this early testimony.
– Evangelical scholars note differences of style between Revelation and the Gospel/epistles but still often affirm common authorship in the person of John (perhaps writing in different circumstances).

Why evangelicals value this authorship
– Eyewitness authority: a living link to Jesus’ teaching and ministry gives the letter weight on doctrine and practice.
– Pastoral credibility: John’s pastoral concern for believers’ assurance, ethical life, and right belief is taken as coming from an apostle who knew Christ personally.
– Doctrinal importance: the epistle addresses core evangelical concerns—Christ’s true incarnation, the necessity of faith and love, and the assurance of salvation.

How this connects to 1 John 5:14–15
– The verses read (NIV): “And this is the confidence we have in approaching God: that if we ask anything according to his will, he hears us. And if we know that he hears us—whatever we ask—we know that we have what we asked of him.”
– From an evangelical perspective, these verses reflect John’s pastoral aims:
– Assurance: believers can have confidence in prayer because God hears his children.
– Condition: the confidence is tied to asking “according to his will” — prayer aligned with God’s revealed purposes (not a promise of getting whatever we selfishly desire).
– Relationship and witnessing: the basis for such confidence is God’s covenantal relationship with believers in Christ, consistent with John’s emphasis on abiding in Christ and living in obedience.
– Practical evangelical application: pray boldly and expectantly, but pray in dependence on God’s revealed will (Scripture), in Christ’s name, and with an attitude of submission to God’s sovereign wisdom.

Further reading (evangelical-friendly)
– Read the short epistle itself (1 John) alongside the Gospel of John to see common themes.
– Accessible commentaries/introductions by evangelical authors (for study and pastoral application) — for example, John Stott’s treatment in the Bible Speaks Today series and treatments by contemporary evangelical New Testament scholars. Also look to trustworthy study Bibles and sermon series by evangelical pastors for pastoral application.

If you’d like, I can:
– Give a short biography of John with biblical references;
– Explain the Greek terms behind the key phrases in 1 John 5:14–15;
– Summarize how different evangelical groups interpret “according to his will” (practical vs. theological perspectives). Which would you prefer?