John Gill Commentary Mark 14:8

"She hath done what she could; she hath anointed my body beforehand for the burying." — Mark 14:8 (ASV)

She has done what she could
What she had in her heart, and in the power of her hands to do; she has done according to her ability, and her good will; and if she had not done it now, she could not have done it at all.

She is come aforehand to anoint my body to the burying ;
or, "as if it was to bury me", as the Syriac version renders it. Christ signifies by this, that he should shortly die, and that this woman came before hand to anoint him, and, as it were, to perform the funeral rites before he was dead; it being revealed to her by the Spirit, that Jesus would quickly die, and she should not be able to perform this good work when dead, and therefore came to do it before; or, at least, she was directed by the Spirit of God, because she would be prevented doing it afterwards; (See Gill on Matthew 26:12).