The primary headword is the future active participle, masculine/neuter genitive singular, of pareggua/w. This form is unattested elsewhere, but may appear here only by scribal error: see n.1 below.
For other forms of the same verb see pi 517 and pi 518.
[1] = Hesychius pi753, Synagoge, Photius pi339 Theodoridis, though these lexica have the headword as paregguh/santos (aorist active participle) rather than the Suda's paregguh/sontos (future active participle). The aorist is surely correct (and the future a scribal error), since the gloss in all these lexica is an aorist active participle. Theodoridis regards paregguh/santos as extracted from Xenophon, Anabasis 4.7.25. Another possibility [DW], given the tastes of the compiler of this part of the Suda, is Josephus, Jewish Antiquities 5.312; cf. pi 513, pi 522.
[2] A paraphrase of Theophylact Simocatta, Histories 5.8.10, also quoted more directly at epsilon 2631. The text of Theophylact reads parenegu/a rather than the Suda's pareneggu/a, exhibiting a late-Greek reanalysis of the stem -eggu- as -en-gu-. The form found in the Suda would thus appear to be a classicizing re-analysis (on the part of the Suda or an intermediary source) of the stem into -en-eggu-. The same process occurs with the next lemma in the entry: see n.3 below.
[3] An approximation of Menander Protector 7.31 (= Constantine Porphyrogenitus, Excerpta de legationibus 450.33). Once again the verb appears in the Menander excerpt as parenegu/hse and has been re-analysed (cf. n.2 above).