Mary took about a pint of pure nard, an expensive perfume; she poured it on Jesus' feet and wiped his feet with her hair. And the house was filled with the fragrance of the perfume. (John 12:3)
Mary's act of devotion is rich in possible meaning. Is Mary preparing Jesus in advance for burial as a prophetic act pointing to Jesus' torture and death? Is the anointing with oil of a king? Perhaps it is simply an act of shocking devotion.
John tells us the perfume is expensive (worth a year's wages). A woman touching a Rabbi, let alone with her hair, would have scandalized many who watched, or later heard about it. Judas, seemingly pragmatic, self-righteously questions the opportunity cost of squandering such an expensive resource. Jesus simply accepts Mary's action as one of devotion.
John never wastes words. In the narrative he makes a point of telling us, the reader/listener, that the house was filled with the fragrance of the perfume. Well, of course. Such an amount in a small, confined space would. Why tell us the obvious? Perhaps John is telling is something at a deeper level. Perhaps we are being reminded that total devotion to Jesus has a beautiful fragrance about it that will fill the space in which we offer it. All who are near will sense it.
We are called to offer nothing less than total devotion to God. We do this in response to the One who gave his all for and to us.