Exegesis:
homoia estin kokkō sinapeōs ‘it is like a mustard seed.’ kokkos sinapeōs also 17.6.
hon labōn anthrōpos ebalen eis kēpon heautou ‘which a man took and put in his garden.’ ballō lit. ‘to throw,’ is used here in a weakened sense, ‘to put.’ The aorist tense of ebalen and the other verbs in v. 19 is gnomic and due to the parable-character of the passage. It does not refer to a past event but to a present reality.
kēpos ‘garden.’
kai ēuxēsen ‘and it grew,’ change of subject. For auxanō cf. on 1.80.
kai egeneto eis dendron ‘and it became a tree.’ ginomai eis with accusative means ‘to become.’
kai ta peteina tou ouranou kateskēnōsen en tois kladois autou ‘and the birds of the air nested in its branches.’ For ta peteina tou ouranou cf. on 8.5.
kataskēnoō ‘to nest.’
klados ‘branch.’
Translation:
A grain of mustard seed, i.e. a single seed of the mustard plant. One should keep in mind that in Rabbinic literature the mustard seed was proverbial for an insignificant size or amount (also in the Koran, S. 21.47; 31.16). A close equivalent in Indonesia is the Brassica juncea (or, rugose), which is botanically related with the Sinapis nigra, has an equivalent function (its leaves being used for spicing food), can reach a length of 1.25 M., and is typical for insignificance (it being said, for instance, in a Malay literary work that heaven and earth are “no bigger than a seed of the brassica when compared with Allah’s Throne”, and in a Balinese proverb that bad people “see the sins of the righteous, although they are as Brassica seeds, but do not see their own sins, although they are as madja-fruits”). In some cases, however, a reference to mustard seed, or to a close botanical and functional equivalent does not fit the context, e.g. because its plant is small, so that it would be ridiculous to say that the birds nestle in its branches, or because another seed is proverbial for insignificance. Then one may consider a generic rendering, such as ‘tiny seed,’ or a cultural equivalent, e.g. seed of a fig tree (used in Yao), or of a banyan tree (suggested but not used in Gujarati)—with an explanatory footnote, if thought necessary. For seed see 8.5.
Which a man took and sowed in his garden is sometimes better changed into a conditional or temporal clause going with what follows, ‘when a man takes it (or, that seed) and sows it in his garden, it grows….’ A man, or, where sowing is not done by men, ‘somebody,’ the sex not being relevant here. For to sow see references on 8.5. Garden, or, ‘field,’ ‘plot of ground.’
It grew, or, using a more specific verb, ‘it sprouted’ (Balinese), or shifting to what comes from the seed, ‘the plant grew.’ Cf. also 1.80.
And became a tree, or, ‘till it had-a-stem’ (Balinese). That tree is used rather hyperbolically may be indicated by saying ‘a tree so to say,’ but a word for ‘bush,’ or, ‘shrub’ may be more appropriate for the plant in question.
The birds of the air, see 8.5.
To make nests, or, ‘to nest,’ ‘to make/have a place to live,’ ‘to live.’
In its branches, or, ‘among its branches/twigs/leafstalks,’ ‘under its leaves,’ etc. depending again on what is normally said in connexion with the plant chosen, or even, ‘in its shade’ (Malay).
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.