{He sighed deeply in his spirit} (anastenaxas t(9369)
pneumati). The only instance of this compound in the N.T. though
in the LXX. The uncompounded form occurs in  Mr 7:34  and it is
common enough. The preposition ana- intensifies the meaning of
the verb (perfective use). "The sigh seemed to come, as we say,
from the bottom of his heart, the Lord's human spirit was stirred
to its depths" (Swete). Jesus resented the settled prejudice of
the Pharisees (and now Sadducees also) against him and his work.
{There shall no sign be given unto this generation} (ei
doth(8873)etai t(8869) gene(8369) taut(8869) s(886d)eion).  Mt 16:4  has simply ou
doth(8873)etai, plain negative with the future passive indicative.
Mark has ei instead of ou, which is technically a conditional
clause with the conclusion unexpressed (Robertson, _Grammar_, p.
1024), really aposiopesis in imitation of the Hebrew use of im.
This is the only instance in the N.T. except in quotations from
the LXX ( Heb 3:11  4:3,5 ). It is very common in the LXX. The
rabbis were splitting hairs over the miracles of Jesus as having
a possible natural explanation (as some critics do today) even if
by the power of Beelzebub, and those not of the sky (from heaven)
which would be manifested from God. So they put up this fantastic
test to Jesus which he deeply resents.  Mt 16:4  adds "but the
sign of Jonah" mentioned already by Jesus on a previous occasion
( Mt 12:39-41 ) at more length and to be mentioned again ( Lu
11:32 ). But the mention of the sign of Jonah was "an absolute
refusal of signs in their sense" (Bruce). And when he did rise
from the dead on the third day, the Sanhedrin refused to be
convinced (see Acts 3 to 5).