The last line of the poem is the most important one and holds the key to the allegorical meaning of the poem. It is only for this last line ‘And miles to go before I sleep’ that the poem has been highly acclaimed. It suggests that we have a lot of things to do before we die. So we cannot stop and watch at a beautiful thing and waste our time. So this line is repeated to emphasize the point the poet wants us to get well.

This question is indeed covered here: https://englicist.com/questions/main-theme-and-message-of-stopping-by-woods

“And miles to go before I sleep” the poet says that he has a lot of things to do in this world before he sleeps. The word sleep here symbolises the final sleep – death.

The last two lines – in fact, the entire “d, d, d, d” rhyme scheme of the closing stanza – is Frost’s brilliant resolution to the rhyme scheme problem he created for himself in the previous stanzas.  It’s brilliant not only because it solved the problem but because it’s both lovely and an evocative echo that’s made legions of readers want to interpret it.

Only Frost knows what, if any, deeper meaning there is to those two lines or, for that matter, the entire poem.  Be careful about any certainty you might feel, because another of his works, The Road Not Taken, is almost universally misinterpreted.

He is making us to know or urging us to know that we should fulfill our promises before we die.

The last line has been repeated to explain the physical magnitude of the journey one has to pass before they lie down for eternal sleep. It refers to completing one’s promises and marking one’s words..