St. Thomas frequently recited this before he dictated, wrote, or preached.

Ineffable Creator,
Who, from the treasures of Your wisdom,
has established three hierarchies of angels,
has arrayed them in marvelous order above the fiery heavens,
and has marshaled the regions of the universe with such artful skill,

You are proclaimed the true font of light and wisdom,
and the primal origin raised high beyond all things.

Pour forth a ray of Your brightness
into the darkened places of my mind;
disperse from my soul the twofold darkness into which I was born:
sin and ignorance.

You make eloquent the tongues of infants.
Refine my speech
and pour forth upon my lips the goodness of Your blessing.

Grant to me
keenness of mind,
capacity to remember,
skill in learning,
subtlety to interpret,
and eloquence in speech.

May you
guide the beginning of my work,
direct its progress,
and bring it to completion.

You Who are true God and true Man,
Who live and reign, world without end.

Amen.