Stephen Carlson wrote:
Luke 2:33 wrote:καὶ ἦν ὁ πατὴρ αὐτοῦ καὶ ἡ μήτηρ θαυμάζοντες ἐπὶ τοῖς λαλουμένοις περὶ αὐτοῦ.
Why is the main verb ἦν singular when the subject ὁ πατὴρ αὐτοῦ καὶ ἡ μήτηρ and the modifying participle θαυμάζοντες are both plural? Is this a case of anacoluthon where the writer was initially thinking about Joseph's amazement and changed syntactic horses mid-stream to include Mary as well?
Also, the combination of the imperfect of εἰμί plus a present participle makes this a possible candidate for an imperfect periphrastic construction. Does the lack of concord in number between the finite verb and the participle, however, point away from viewing this verb as containing an imperfect periphrastic?
It seems to me that BDF adequately speaks to this arrangement of elements: (a) singular verb when there's an added subject with verb preceding the first subject; (b) "Attributives (participles) which belong to two or more connected substantives customarily agree with the nearest."; (c) periphrastic forms with εἶναι very commonly used by Lk and Mk, emphatic and probably representing Semitic influence.
(4) Agreement with Two or More Co-Ordinate Words
135. Connected by και (ἤ). Regarding agreement with two or more subjects connected by καί, the same loose rules are valid for the NT as for classical usage. The following examples with persons as subject may be noted: (1) When the subject consists of sing. + sing. or of sing. + plur. the verb agrees (a) with the first subject if the verb stands before it, except when the subject-group is basically conceived as a whole; (b) with both subjects taken together if the verb stands after the second subject; (c) with the first if the verb stands between; (d) rules (a) and (b) can be combined when a finite verb stands before and a participle after the group, or the reverse. (2) When one of the two subjects is a 1st plur., the verb is in the 1st plur. and modifiers which refer to the subject are in the nominative plur.; such modifiers are in the masculine even when the subject group combines masculine and feminine. (3) Attributives (participles) which belong to two or more connected substantives customarily agree with the nearest. (4) The sing. is regularly used with two sing. subjects connected by ἤ (as in English but contrary to German).
353. Forms of εἶναι with a present participle are widely employed in the NT as periphrases: ἦν for the imperfect; ἔσομαι for the future; εἰμί rarely for the present indicative; and sometimes εἶναι for the infinitive and ἴσθι for the present imperative. (1) Some parallels can be cited from the classical language (K.–G. I 38ff. n. 3; Rosenkranz IF 48  162f.); it can also be maintained that this mode of expression is analogous to the use of periphrasis in the perfect system (§352; cf. φλεγόμενοι ἦσαν … καὶ βεβλημένοι ApocP 27) and that its use in the future makes it possible to express linear action. Since, however, the Hellenistic language (even the more vernacular of the papyri) is familiar with this development only to a very limited degree (Schmid III 112ff.; Mlt. 226f. [358f.]; Mayser II 1, 223f.; Widmann 135) and since, on the other hand, the frequency of NT examples is highest in Lk (Gospel and first half of Acts) then Mark (less in Mt), this idiom, which is just possible in Greek, was at least strongly supported by the extensive Semitic use of such periphrases, especially in the imperfect (Debrunner, IF 58  313). A certain emphasis in periphrasis, which is the rule in classical examples, is also often unmistakable in the NT.
Blass, F., Debrunner, A., & Funk, R. W. (1961). A Greek grammar of the New Testament and other early Christian literature (179). Chicago: University of Chicago Press.