Exegesis:

ei echete … elegete an ‘if you had … you would say,’ implying that they do not have faith even like a mustard-seed.Translation commentary on Luke

pistin hōs kokkon sinapeōs ‘faith like a mustard seed,’ i.e. a very small amount of faith. For kokkos sinapeōs cf. on 13.19.

tē sukaminō [tautē] ‘to this mulberry tree,’ presumably a tree close to the speaker.

sukaminos ‘mulberry tree’; exact meaning uncertain.

ekrizōthēti kai phuteuthēti en tē thalassē lit. ‘be uprooted and be planted in the sea,’ here best understood as reflexive, ‘pull up yourself by the roots and plant yourself in the sea.’

ekrizoō ‘to uproot,’ ‘to pull out by the roots.’

kai hupēkousen an humin ‘and it would obey you at once.’ The shift from the imperfect (elegete an) to the aorist points to an immediate result. hupakouō, cf. on 8.25.

Translation:

As a grain of mustard seed, or making explicit the reference to (small) size, ‘the size of a mustard seed’ (Kekchi), ‘(even) as little as a (grain of) mustard seed.’ For mustard seed see 13.19.

Sycamine tree. Simply to say ‘tree’ (Leyden, Sranan Tongo, one West Nyanja version), ‘big tree’ (Tae’), is acceptable here because the kind of tree is not of special relevance in the context.

Be rooted up, and be planted in the sea, or, to avoid an imperative and/or a passive form, ‘you shall be uprooted and shall be planted,’ ‘you must pull yourself out by the roots and plant yourself in the sea.’ To uproot, or, ‘to pull out’ (Bahasa Indonesia, Balinese), ‘to pull loose from the ground’ (Sranan Tongo). Be planted may have to be rendered, ‘be set’ (Zarma), ‘go and stand,’ ‘grow’ (Toraja-Sa’dan).

For to obey see on “obedient” in 2.51.

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.