There are five "Faithful Sayings" in the Pastoral Epistles, each introduced or concluded with the phrase πιστὸς ὁ λόγος. They are: 1Ti 1.15; 1Ti 3.1; 1Ti 4.9; 2Ti 2.11; Tt 3.8. At least, those are the verses that πιστὸς ὁ λόγος occurs in.

Several times, Rev 22.6 is offered as a cross-reference, primarily because the words λόγος and πιστὸς are related:

καὶ εἶπεν μοι· οὗτοι οἱ λόγοι πιστοὶ καὶ ἀληθινοι ... , which is translated in the ESV as "And he said to me, 'These words are trustworthy and true. ... ' (Rev 22.6, ESV)

In church this past Sunday, the message was on Heb 10.19-23. Check out verse 23:

κατέχωμεν τὴν ὁμολογίαν τῆς ἐλπίδος ἀκλινῆ, πιστὸς γὰρ ὁ ἐπαγγειλάμενος, — in the ESV, this is "Let us hold fast the confession of our hope without wavering, for he who promised is faithful." (Heb 10.23, ESV)

As regards vocabulary, Rev 22.6 is the better cross-reference. But as regards structure and grammatical concept, wouldn't Heb 10.23 be a better cross reference? Take out the post-positive γὰρ and it is a dead-on match: πιστὸς plus ὁ plus [masc. nom. sing. substantive]. Right?

• πιστὸς ὁ λόγος
• The saying is trustworthy or Faithful is the word
• πιστὸς γὰρ ὁ ἐπαγγειλάμενος
• for he who promised is faithful or perhaps Faithful is the promiser or even The promiser is trustworthy

I haven't done much examination of commentaries relative to this exact reference (Heb 10.23), but as I recall one issue that is generally raised is the lack of use of similar vocabulary or structure in the NT but the repeated use of πιστὸς ὁ λόγος in the Pastorals. It seems fishy to many folks who posit a later date for the Pastorals. Makes me wonder if they've examined πιστὸς ὁ λόγος in light of πιστὸς γὰρ ὁ ἐπαγγειλάμενος in Heb 10.23

I'll have to check and see if Knight handles it.

Wayne Leman of the Better Bibles Blog posts a link to Kenny Pearce's blog, where Kenny (whom I'm unfamiliar with) has a question about 2Ti 2.2.

In his entry, Kenny writes:

This past week, Steven and I were rather perplexed by the way in which the standard translations have chosen to render 2Ti 2.2, and had some difficulty connecting the translations to the Greek. NKJV renders this verse, "And the things you have heard from me among many witnesses, commit these to faithful men who will be able to teach others also." The relevant portion, "the things you have heard from me among many witnesses," is rendered almost identically by the other translations. NIV: "the things you have heard me say in the presence of many witnesses," ESV: "what you have heard from me in the presence of many witnesses." The trouble is that the Greek seems to suggest a reading more like "the things which you have heard from me through many witnesses." That is, the Greek appears to say that Timothy heard these teachings from many witnesses who came from Paul, rather than that he heard them from Paul himself. The following is my (mostly failed) attempt to make sense of this.

George W. Knight's NIGTC volume is, as far as I am concerned, the best available critical commentary available that seriously interacts with the Greek text.

Mounce (WBC) is good. Knight is better. Knight deals directly with morphological and syntactical issues when necessary and doesn't have the broad structure of WBC to bog him down. He doesn't get into the contemporary citations so much, but again the focus helps him. If you plan to work through the Greek text, then Knight (combined with SIL's Exegetical Summaries) is your friend.

Ellicott's commentary hails from the late 19th century, but don't let that scare you away. The commentary is on the Greek directly. I'm not sure of the Greek edition, though. I'd thought it was Tischendorf's editio octava maior, but I can't confirm that at present. Perhaps it is Textus Receptus.

Either way, Ellicott's work is worth examining, primarily because he really is commenting critically on the language. He also brings in readings from Latin, Syriac and Gothic and examines them along with the Greek where he deems appropriate. He references readings from various uncial texts frequently. There are several references to classical Greek works as well.

His Revised Translation is his attempt to update the KJV. Most helpful in this translation is his apparatus of alternate English readings, with several English versions represented.