A.T. Robertson Commentary 1 Corinthians 14:6

"But now, brethren, if I come unto you speaking with tongues, what shall I profit you, unless I speak to you either by way of revelation, or of knowledge, or of prophesying, or of teaching?" — 1 Corinthians 14:6 (ASV)

If I come (εαν ελθω). Third class condition, supposable case (aorist subjunctive).

What shall I profit you (τ υμας ωφελησω). Two accusatives with this verb .Unless I speak (εαν μη λαλησω). Second condition (also third class) with the one conclusion (cf. 1 Timothy 2:5).