But we were gentle in the midst of you (alla egenēthēmen nēpioi en mesōi humōn). Note egenēthēmen (became), not ēmetha (were). This rendering follows ēpioi instead of nēpioi (Aleph B D C Vulg. Boh.) which is clearly correct, though Dibelius, Moffatt, Ellicott, Weiss prefer ēpioi as making better sense. Dibelius terms nēpioi unmoglich (impossible), but surely that is too strong. Paul is fond of the word nēpioi (babes). Lightfoot admits that he here works the metaphor to the limit in his passion, but does not mar it as Ellicott holds.
As when a nurse cherishes her own children (hōs ean trophos thalpēi ta heautēs tekna). This comparative clause with hōs ean (Mar 4:26; Gal 6:10 without ean or an) and the subjunctive (Robertson, Grammar, p. 968) has a sudden change of the metaphor, as is common with Paul (1Ti 5:24; 2Co 3:13.) from babes to nurse (trophos), old word, here only in the N.T., from trephō, to nourish, trophē, nourishment. It is really the mother-nurse “who suckles and nurses her own children” (Lightfoot), a use found in Sophocles, and a picture of Paul’s tender affection for the Thessalonians. Thalpō is an old word to keep warm, to cherish with tender love, to foster. In N.T. only here and Eph 5:29.