{In the meantime} (en hois). It is a classic idiom to
start a sentence or even a paragraph as here with a relative, "in
which things or circumstances," without any expressed antecedent
other than the incidents in  11:53f . In  12:3  Luke actually
begins the sentence with two relatives anth' h(936e) hosa
(wherefore whatsoever). {Many thousands} (muriad(936e)). Genitive
absolute with episunachtheis(936e) (first aorist passive participle
feminine plural because of muriad(936e)), a double compound late
verb, episunag(935c), to gather together unto. The word "myriads" is
probably hyperbolical as in  Ac 21:20 , but in the sense of ten
thousand, as in  Ac 19:19 , it means a very large crowd
apparently drawn together by the violent attacks of the rabbis
against Jesus. {Insomuch that they trode one upon another}
(h(9373)te katapatein all(886c)ous). The imagination must complete the
picture of this jam. {Unto his disciples first of all} (pros
tous math(8874)as autou pr(9374)on). This long discourse in  Lu 12  is
really a series of separate talks to various groups in the vast
crowds around Jesus. This particular talk goes through verse
 12 . {Beware of} (prosechete heautois apo). Put your mind
(
oun understood) for yourselves (dative) and avoid (apo with
the ablative). {The leaven of the Pharisees which is hypocrisy}
(	(8873) zum(8873) h(8874)is estin hupocrisis t(936e) Pharisai(936e)). In  Mr 8:15 
Jesus had coupled the lesson of the Pharisees with that of Herod,
in  Mt 16:6  with that of the Sadducees also. He had long ago
called the Pharisees hypocrites ( Mt 6:2,5,16 ). The occasion was
ripe here for this crisp saying. In  Mt 13:33  leaven does not
have an evil sense as here, which see. See  Mt 23:13  for
hypocrites. Hypocrisy was the leading Pharisaic vice (Bruce) and
was a mark of sanctity to hide an evil heart.