Matt 7:13 εισελθετε

As in Matt 2:5 ειπον and Matt 5:1 προσηλθον, here some manuscripts (ℵ B C L N O W Δ Θ Σ Φ f13 33. 1424 al) and editors (Bover, Greeven, Lachmann, Merk, Soden, Tischendorf, Vogels) favor the supposedly Alexandrian spelling εισελθατε (with an -α-) over the more common spelling εισελθετε (with an -ε-), represented by most manuscripts (including E G K M S U V X Π Ω [047] 0211 Byz f1.35 565. 1500. 2224).  Wordsworth (25) notes that εισελθατε is an alteration in favor of the Alexandrian pronunciation, which, for example, favors the first person singular forms ἔφυγα, ἔλαβα, and εἶδα (for ἔφυγον, ἔλαβον, and εἶδον, respectively) and the third person plural forms ἔφυγαν, ἔλαβαν, εἶδαν, εὗραν, ἦλθαν, εἶπαν (for ἔφυγον, ἔλαβον, εἶδον, εὗρον, ἦλθον, and εἶπον, respectively). That particular phenomenon perhaps developed and was popularized to distinguish the otherwise identical first person singular and third person plural forms. But there is little reason to suppose that the NT authors would have preferred the "Alexandrian" forms any more than they would the common ones. For many examples of sporadic alterations away from the -ο- form toward the "Alexandrian" -α- form in primary Alexandrian witnesses, see Soden, 1:1392. From the same source, several examples more directly related to the present case of εισελθετε vs. εισελθατε include:

Matt 6:10 - ελθατω (ℵ D G W Δ)
Matt 10:13 - ελθατω in (ℵ C L N W f13 33)
Matt 26:39 - παρελθατω (p37vid ℵ A C D E F G H L Δ Θ Ω 33)
Mark 13:15 - εισελθατω (ℵ A D L Δ f13)
Luke 11:2 - ελθατω (p75 ℵ C P W Δ f13)
2 Cor 6:17 - εξελθατε (p46 ℵ B C F G 33)
Rev 18:4 - εξελθατε (ℵ A)

Trivialities of this sort generally play little role in New Testament textual criticism, except perhaps in the chance that the provenance of a manuscript might be guessed by means of attention to such matters.