The picture of water or oil or the Holy Spirit coming upon a head and soaking down the body is a common one in Scripture. Kings, prophets and priests were all anointed with oil before taking up office. The Holy Spirit fell at Pentecost on the heads of the waiting disciples.
The Psalmist took up this image and related that the dew of Mt Hermon, standing as the highest point in Israel, was the crowning point from which God’s blessings spread over Israel and that this stood as an allegory for everlasting blessings when God’s people are in unity (Psa. 133).
Then we come to the story of Mary, the sister of Lazarus (John 12:3) taking a container of very expensive fragrant oil and breaking its seal and pouring the oil over the head of Jesus as He sat at the table (Matt. 26:7).
She wasn’t anointing Jesus for the office of prophet, priest or king – the Holy Spirit had already done that at His baptism and she wasn’t qualified to make that call, anyway. She was expressing her devotion to her Master: she was pouring her heart out in gratitude for what He was about to accomplish on her behalf.
Only when the seal on our heart has been broken by knowing Jesus and the wonderful gift of salvation that He has given us, can we pour out a beautiful perfume. Jesus understood her motives and this is why he remarked, “Let her alone; she has kept this for the day of My burial” (John 12:7).
Our lives can only bring forth the fragrance at great cost. The cost is our all. We can withhold nothing before the One who loved us with His all.
Love draws us into the most outrageously extravagant acts of devotion. Love is utterly unexplainable. The Father first loved us with this extravagant and unconditional love and that's why we love Him and we love each other in the same way (1 John 4:19).
(All quotes are from the NKJV).