For as Jonas was three days and three nights in the whale's belly; so shall the Son of man be three days and three nights in the heart of the earth.
This is NOT a reference to Christ being in the grave for three days and three nights. We know from Biblical evidence that he did NOT spend three days and three nights in the grave (Luke 13:32; Luke 18:33). Not only that, but His body would have started to decay if he had spent three days and three nights in the grave. According to the testimony of Peter, which was recorded by Luke, Jesus' body was not left in the grave long enough for it to start the decay process (Acts 2:27). The oils used to embalm Jesus' dead body were not embalming oils to preserve a body. They were sweet smelling oils which were traditionally used to mask the scent as bodies decayed. Usually those oils are applied to a dead body - not a living body, but Mary thought it best to use that oil on the Living Christ, while He could appreciate it, instead of on a dead Christ. This was why Jesus made the strange statement, "For in that she hath poured this ointment on my body, she did it for my burial" (Matthew 26:12).
By anointing Jesus for His burial two days before His death, Mary had essentially, and symbolically buried Jesus "in the heart of the earth" (Mark 14:1-3).