What is the fig tree curse about?

His Cursing the Barren Fig-Tree

Mark  11:12-14

Here is,

I.  Christ's cursing the fruitless fig-tree. He had a convenient resting-place at Bethany, and therefore thither he went at resting-time; but his work lay at Jerusalem, and thither therefore he returned in the morning, at working-time; and so intent was he upon his work, that he went out from Bethany without breakfast, which, before he was gone far, he found the want of, and was hungry (v. 12), for he was subject to all the sinless infirmities of our nature. Finding himself in want of food, he went to a fig-tree, which he saw at some distance, and which being well adorned with green leaves he hoped to find enriched with some sort of fruit. But he found nothing but leaves; he hoped to find some fruit, for though the time of gathering in figs was near, it was not yet; so that it could not be pretended that it had had fruit, but that it was gathered and gone; for the season had not yet arrived.

Or, He found none, for indeed it was not a season of figs, it was no good fig-year. But this was worse than any fig-tree, for there was not so much as one fig to be found upon it, though it was so full of leaves. However, Christ was willing to make an example of it, not to the trees, but to the men, of that generation, and therefore cursed it with that curse which is the reverse of the first blessing, Be fruitful; he said unto it, Never let any man eat fruit of thee hereafter for ever, v. 14. Sweetness and good fruit are, in Jotham's parable, the honour of the fig-tree (Judges 9:11), and its serviceableness therein to man, preferable to the preferment of being promoted over the trees; now to be deprived of that, was a grievous curse.

II . This was intended to be a type and figure of the doom passed upon the Jewish church, to which he came, seeking fruit, but found none (Luke 13:6, 7); and though it was not, according to the doom in the parable, immediately cut down, yet, according to this in the history, blindness and hardness befel them (Romans 11:8, 25), so that they were from henceforth good for nothing. The disciples heard what sentence Christ passed on this tree, and took notice of it. Woes from Christ's mouth are to be observed and kept in mind, as well as blessings.

Matthew Henry's Commentary on the Whole Bible.