Now the disciples had forgotten to take bread - See all this, to Mark 8:21, explained at large on Matthew 16:4-12 (note). In the above chapter, an account is given of the Pharisees, Sadducees, and Herodians.

Now the disciples had, forgotten to take bread,.... At Dalmanutha, or Magdala, or whatever place in those parts they were at, before they took shipping, as was their usual method.
Neither had they in the ship with them more than one loaf; for thirteen passengers of them. The Persic version reads the whole thus: "and they forgot to take bread with them, not indeed one loaf, and there was no bread with them in the ship"; See Gill on Matthew 16:5.

Now the disciples had forgotten to take bread, neither had they in the ship with them more than one loaf--This is another example of that graphic circumstantiality which gives such a charm to this briefest of the four Gospels. The circumstance of the "one loaf" only remaining, as WEBSTER and WILKINSON remark, was more suggestive of their Master's recent miracles than the entire absence of provisions.

The disciples had forgotten to take bread. For notes on the warning against the leaven of the Pharisees and Herod, see Matthew 16:5-12. Matthew says "Sadducees" instead of "Herod." Herod was a Sadducee, and the Sadducees generally were his supporters.