A.T. Robertson Commentary Hebrews 13:1

"Let love of the brethren continue." — Hebrews 13:1 (ASV)

Brotherly love (φιλαδελφια). Late word from φιλαδελφος (1 Peter 3:8). See 1 Thessalonians 4:9. It is always in order in a church.

To show love unto strangers (της φιλοξενιας). Old word for hospitality, from φιλοξενος (1 Timothy 3:2), in N.T. only here and Ro 12:3. In genitive case with επιλανθανεσθε (present middle imperative, cf. Hebrews 6:10).

Have entertained angels unawares (ελαθον ξενισαντες αγγελους). Second aorist active indicative of λανθανω, old verb to escape notice and first aorist active participle of ξενιζω, old verb to entertain a guest (ξενος, stranger), according to a classic idiom seen with λανθανω, τυγχανω, φθανω, by which the chief idea is expressed by the participle (supplementary participle), here meaning, "some escaped notice when entertaining angels." The reference is to Ge 18; 19 (Abraham and Sarah did this very thing).