Mark 8:19
When I brake the five loaves among five thousand, how many baskets full of fragments took ye up? They say unto him, Twelve.
Cross-references
Mark 8:8 gives the result of the second feeding (seven baskets), contrasting with the twelve in Jesus' question. Same pattern, different number.
Mark 6:38-44 records the feeding of 5000 itself, providing the event Jesus references here about five loaves and twelve baskets.
Mark 6:43 records the exact result Jesus refers to — twelve baskets from the 5000. Direct reference to that miracle.
Matthew 14:17-21 gives Matthew's account of the same feeding of 5000, with identical numbers of loaves and baskets.
Luke 9:12-17 records the same miracle of feeding 5000, confirming the details Jesus asks about.
John 6:5-13 provides John's version of the feeding of 5000, including the twelve baskets of leftovers.
Matthew 15:37 describes the feeding of 4000 with seven baskets, a different but similar miracle Jesus also references later in this discourse.
Luke 9:17 is a parallel account of the same feeding of 5000, confirming the twelve baskets of leftovers.
John 6:9 provides the source of the five loaves and two fish, adding detail to the miracle Jesus recalls.