I did a web search using 'ash wednesday poem' and basically up popped T S Elliott's long and complicated work.  So I tried again with 'lent poetry' and that was more successful.  Here is one that seemed quite fitting for the start of Lent, that challenges the white-washed tombs nature of strict outward obervance and inner corruption...

Lent

by

Robert Herrick

Is this a Fast, to keep
the larder leane?
and deane
from fat of Veales and Sheep?

Is it to quit the dish
of Flesh, yet still
to fill
the platter high with fish?

Is it to fast an houre
or rag’d go,
or show
a down cast look, and sour?

No: ‘tis a fast, to dole
thy sheaf of wheat
and meat
unto the hungry soule.

It is to fast from strife,
from old debate
and hate:
to circumcise thy life.

To shew a heart grief-rent;
to starve thy sin,
not Bin
and that’s to keep thy Lent.

What does the LORD require of thee, this only this: to do justice, to love mercy and to walk humbly with thy God.

When you fast.... wash your face, comb your hair.... and smile (CG paraphrase of JC!)