In plain words
One who teaches this supreme secret among My bhaktas, holding supreme Bhakti to Me, shall without doubt come to Me alone.
Word for word
He who will teach this supreme secret among My devotees, having made supreme devotion to Me, will come to Me alone, without doubt.
The commentators
Bhagavadgītābhāṣyam
सम्प्रदायस्य कर्तुः फलम् इदानीम् आह —
यः इमं यथोक्तं परमं परमनिःश्रेयसार्थं केशवार्जुनयोः संवादरूपं ग्रन्थं गुह्यं गोप्यतमं मद्भक्तेषु मयि भक्तिमत्सु अभिधास्यति वक्ष्यति, ग्रन्थतः अर्थतश्च स्थापयिष्यतीत्यर्थः, यथा त्वयि मया । भक्तेः पुनर्ग्रहणात् भक्तिमात्रेण केवलेन शास्त्रसम्प्रदाने पात्रं भवतीति गम्यते । कथम् अभिधास्यति इति, उच्यते — भक्तिं मयि परां कृत्वा ‘भगवतः परमगुरोः अच्युतस्य शुश्रूषा मया क्रियते’ इत्येवं कृत्वेत्यर्थः । तस्य इदं फलम् — मामेव एष्यति मुच्यते एव । असंशयः अत्र संशयः न कर्तव्यः ॥ ६८ ॥
In plain words
Now he states the fruit that comes to the one who carries this tradition forward:
Whoever declares this teaching — as it was given, supreme, aimed at the highest good, this dialogue of Keśava and Arjuna, secret and precious — among my devotees, among those who hold devotion toward me, will be establishing it, both in its words and in its meaning, exactly as I have given it to you. Notice that 'devotion' is named again here — that tells us devotion alone, nothing more, is enough to qualify someone to pass this teaching on. And how should it be declared? By first bringing supreme devotion toward Me, holding the thought, 'I am serving the Blessed Lord, my highest teacher, the imperishable one' — and speaking from there. And the fruit of doing this is simple: that person comes to Me alone — which is to say, is freed. Have no doubt about this at all.
Close to the Sanskrit
Of the maker of the tradition, the fruit — now he states:
He who will declare — will speak — this text, as stated, supreme, whose purpose is the supreme good, in the form of the dialogue of Keśava and Arjuna, secret, most worthy to be guarded, among my devotees, among those possessing devotion toward me — that is, will establish [it], in terms of the text and in terms of its meaning, this is the meaning — as [it was declared] in you by me. Because of the repeated mention of 'devotion,' it is understood that by devotion alone, unaided, one becomes a fit recipient for the transmission of this teaching. How will he declare it? — it is answered: having made supreme devotion toward me — thinking, 'service to the Blessed Lord, the supreme teacher, the imperishable, is performed by me' — thus, having done so, this is the meaning. Of that [act] this is the fruit — he will come to me alone, he is simply liberated. Without doubt: here doubt is not to be entertained.