(12) There shall no sign be given.--We note the omission of "the sign of the prophet Jonas," as given in Matthew 16:4.

Verse 12. - He sighed deeply in his spirit (ἀναστενάξας) Another graphic touch of this evangelist; such as he had learnt in all probability from St. Peter. The word occurs nowhere but here. It is the outcome of grief and indignation, in which, however, grief predominates. There shall no sign be given unto this generation (εἰ δοθήσεται σημεῖον). This is a Hebrew idiom, based upon a form of taking an oath which prevailed amongst the Jews. The full form would be, "God do so and so to me, if so and so." Hence the hypothetical part of the clause came to be used alone, expressing a very strong form of denial or refusal.

8:11-21 Obstinate unbelief will have something to say, though ever so unreasonable. Christ refused to answer their demand. If they will not be convinced, they shall not. Alas! what cause we have to lament for those around us, who destroy themselves and others by their perverse and obstinate unbelief, and enmity to the gospel! When we forget the works of God, and distrust him, we should chide ourselves severely, as Christ here reproves his disciples. How is it that we so often mistake his meaning, disregard his warnings, and distrust his providence?And he sighed deeply in his Spirit,.... In his human soul; and which shows that he had one, and was subject to grief and sorrow, and all passions and infirmities, excepting sin. This deep sigh was on account of the hardness of their hearts, the malignity of their minds, and insincerity of their intentions; who had no view to come at truth by this inquiry, but to ensnare him:

and saith, why doth this generation seek after a sign? when so many have been shown among them, and they will not believe:

verily I say unto you, there shall no sign be given to this generation: such as they desired; namely, one from heaven. The Evangelist Matthew adds, "but the sign of the Prophet Jonas"; See Gill on Matthew 16:4, Matthew 12:40.