STRONGS NT 4517a: σ [σ ,Sigma: the practice (adopted by Griesbach, Knapp, others, after H. Stephanus, et al.) of employing the character sigma σ in the middle of a compound word has been abandoned by the recent critical editors; cf. Winers Grammar, § 5, the passage cited; Lipsius, Gram. Untersuch., p. 122; Matthiae, § 1 Anm. 5; Alexander Buttmann (1873) Ausf. Sprchl. § 2 Anm. 3; Kühner, § 1 Anm. 1. Tdf. edition 8 writes sigma ς' also even at the end of a word, after the older manuscripts. On movable final sigma ς' see ἀχρἱσ', μεχρἱσ', ὁυτὡσ'. The (Ionic) combinations ῥς for ῥρ, and σς for ττ (cf. Fischer, Animadvers. ad Veller. etc. i., pp. 193f, 203; Kühner, § 31, pp. 124, 127), have become predominant (cf. ἄρσην, θαρσέω, θάρσος, ἀπαλλάσσω etc., γλῶσσα, ἥσσων (which see), θάλασσα, κηρύσσω, περισσός, πράσσω (which see), τάσσω, τέσσαρες, φυλάσσω, etc.), except in a few words, as κρείττων (which see), the derivatives of ἐλαττῶν (of which word both forms are used indiscriminately), ἥττημα, ἡττάω (yet see 2 Corinthians 12:13), etc.; cf. Buttmann, 7. Some proper names are spelled indifferently with one sigma ς' or with two; as, Ἐλισ῾σ᾿αιος. Zeta ζ' is occasionally substituted for sigma ς', especially before mu μ', see σβέννυμι, Σμύρνα (σμύρνα, cf. Sophocles Glossary, § 58, 3, and Lexicon, under the word; Tdf. Proleg., p. 80; WHs Appendix, p. 148; Buttmann, 5; Alexander Buttmann (1873) Ausf. Sprchl. § 3 Anm. 6; Bezae manuscript, Scrivener edition, p. xlviii.; Liddell and Scott, under the word Zeta ζ', I. 3, and Sigma ς', II. 14 c.); so also xi Ξ, as ξυμβαίνω 1 Peter 4:12 Rbez cf. Kühner, § 325, 5; Alexander Buttmann (1873) Ausf. Spr. as above; see ξύν.]

Ἔρρωσθε appears once in the Greek New Testament, closing the Jerusalem Council’s circular letter (Acts 15:23-29) that was hand-delivered to Antioch and the surrounding Gentile congregations. Positioned at the very end of the correspondence, the word serves as both a formal goodbye and an exhortation to spiritual strength and health.

Literary Background of the Salutation

In Greco-Roman epistolary custom, a brief closing imperative such as ἔρρωσο (singular) or Ἔρρωσθε (plural) was the conventional way to end a letter. While it literally meant “be strong” or “be in good health,” it functioned idiomatically as “farewell.” By employing the common Greek closing rather than a Hebrew style, the apostles communicated in language familiar to their predominantly Gentile recipients, underscoring the international reach of the gospel without compromising its Jewish roots.

Theological Themes Evoked by “Ἔρρωσθε”

1. Spiritual Fortitude: The closing blends physical well-being with moral vigor, echoing the biblical conviction that true strength comes from the Lord (Ephesians 6:10; 2 Timothy 2:1).
2. Covenant Blessing: After outlining essential abstentions (Acts 15:29), the imperative signals confidence that obedience will lead to spiritual health—“You will do well to avoid these things. Farewell.” (Acts 15:29).
3. Apostolic Authority and Care: Far from a perfunctory sign-off, Ἔρρωσθε embodies pastoral concern, assuring the churches that the Jerusalem leaders desired their ongoing welfare.

Acts 15:29 in the Life of the Early Church

The Council’s decree resolved a potentially church-splitting controversy over circumcision and Mosaic regulations. By ending with Ἔρρωσθε, the apostles framed their instructions not as heavy burdens but as safeguards for vibrant fellowship. The response in Antioch—“they rejoiced at the encouragement” (Acts 15:31)—confirms that the recipients felt strengthened, precisely what the closing word wished for them.

Related Biblical Motifs of Strength and Well-Being

• Joshua 1:9 calls God’s servant to “be strong and courageous,” foreshadowing the New Testament’s emphasis on Spirit-empowered strength.
• 1 Corinthians 16:13; Philippians 4:13 echo the same imperative mood, urging believers to stand firm in faith.
• 3 John 2 links physical health and spiritual prosperity, mirroring the holistic sense carried by Ἔρρωσθε.

Historical Usage Outside the New Testament

Papyri and inscriptions from the first century employ ἔρρωσο/Ἔρρωσθε in both formal and personal letters. This everyday salutation lent the apostolic decree cultural accessibility while allowing the writers to infuse a common phrase with distinctly Christian substance.

Pastoral and Devotional Applications

• Concluding Communication: Modern ministry letters, emails, and sermons may appropriately end with a biblical blessing that goes beyond mere politeness, intentionally speaking strength into the reader’s life.
• Unity in Essentials: The word’s placement after the Council’s summary reminds leaders to couple doctrinal clarity with sincere encouragement.
• Prayer Focus: Intercession for fellow believers should include petitions for both spiritual resilience and bodily health, reflecting the holistic concern embedded in Ἔρρωσθε.

Thus, though brief, Strong’s Greek 4517 supplies a window into apostolic shepherding, bridging cultural convention and gospel conviction in a single imperative: “Be strong—farewell.”