Exegesis:

baptisma de echō baptisthēnai ‘but I have a baptism to be baptized with.’ baptisma is emphatic: before the fire can be kindled Jesus has to undergo a baptism. For baptism as a metaphor of suffering.

pōs sunechomai heōs hotou telesthē ‘how I am distressed till it is accomplished!,’ i.e. ‘till it is over.’ For sunechomai cf. on 4.38. The subject of telesthē is baptisma, and the clause refers to a situation that is to come about. For teleō cf. on 2.39.

Translation:

I have a baptism to be baptized with, or, ‘I have a baptism to undergo/receive,’ ‘I have to be baptized in a certain way,’ or shifting to a simile, ‘I have to be immersed/bathed as at baptism (or, as though I were baptized),’ cf. ‘I must begin by being submerged by the baptism I shall be done’ (Shona 1966). If the term and/or the ritual do not have a clear association with immersion in water, an explanatory note referring the reader to Mk. 1.9f, Acts 8.36-39, may be useful. Where the figure of speech would be incomprehensible the non-figurative meaning may have to be added, e.g. ‘I have to be plunged in suffering as a person is plunged in water when he is baptized’ (or in active construction with indefinite agent). For baptism, baptized see 3.3.

I am constrained, or, ‘I feel oppressed,’ ‘my mind is-in-straits’ (Balinese), ‘my-heart (is) restless’ (Bahasa Indonesia RC).

Until, cf. 1.20.

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.