See this passage explained in Matthew 16:1-12.

And the Pharisees came forth,.... Out of their houses; who dwelt in the coasts of Magdala, and parts of Dalmanutha, and came to Jesus, hearing of his being arrived in their neighbourhood:

and began to question with him; or to dispute with him, it being their manner to carry on disputations by questions and answers. The Persic version has the question they put, and about which they disputed, "if thou art the Christ"; in proof of which they required a sign:

seeking of him a sign from heaven, tempting him; See Gill on Matthew 16:1.

Began

The beginnings of things seem to have a peculiar interest for Mark. See Mark 1:1, Mark 1:45; Mark 4:1; Mark 5:17, Mark 5:20; Mark 6:2, Mark 6:7, Mark 6:34, Mark 6:55.

Sign (σημεῖον)

See on Matthew 11:20. Wyc., token. As applied to the miracles of our Lord, this word emphasizes their ethical purport, as declaring that the miraculous act points back of itself to the grace and power or divine character or authority of the doer.

{1} And the Pharisees {b} came forth, and began to question with him, seeking of him a sign from heaven, tempting him.

(1) The stubborn enemies of the doctrine of the Gospel, giving no credit to the miracles already done, require new ones: but Christ, being angry with them, utterly forsakes them.

(b) A common saying which the Hebrews use, by which is meant that the Pharisees went from their houses to purposely engage him.

8:11-13 The Pharisees came... seeking from him a sign from heaven. See notes on Mt 16:1-4.

8:11 Tempting him - That is, trying to ensnare him. Mt 16:1.

11. seeking of him a sign from heaven, tempting him-not in the least desiring evidence for their conviction, but hoping to entrap Him. The first part of the answer is given in Matthew alone (Mt 16:2, 3): "He answered and said unto them, When it is evening, ye say, It will be fair weather; for the sky is red. And in the morning, It will be foul weather to-day: for the sky is red and lowering [sullen, gloomy]. Hypocrites! ye can discern the face of the sky; but can ye not discern the signs of the times?" The same simplicity of purpose and careful observation of the symptoms of approaching events which they showed in common things would enable them to "discern the signs of the times"-or rather "seasons," to which the prophets pointed for the manifestation of the Messiah. The scepter had departed from Judah; Daniel's seventy weeks were expiring, &c.; and many other significant indications of the close of the old economy, and preparations for a freer and more comprehensive one, might have been discerned. But all was lost upon them.

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?