These lines are spoken by Helena at the end of the first scene of Shakespeare's A Midsummer Night's Dream.
At the beginning of the play, Helena is in love with Demetrius—who once wooed her—but he is now in love with Hermia. Hermia is in love with Lysander, but Theseus (Duke of Athens) agrees with Hermia's father, Egeus, that Hermia should be married to Demetrius, the man Egeus has chosen for her.
Hermia protests to the Duke that her father should not consider her feelings in the matter or her feelings for Lysander:
HERMIA: I would my father look'd but with my eyes. (1.1.58)
The Duke responds that no matter what Hermia's feelings toward Lysander are, she should respect her father's wishes and marry Demetrius:
THESEUS: Rather your eyes must with his judgment look. (1.1.58–59)
This exchange of lines sets up a motif that Shakespeare explores throughout the play to reinforce the theme that "love is blind." When a person is in love, that person becomes irrational and unreasonable, and they see what they want to see, either in another person or in a particular situation.
Talking with Lysander later in the scene, Hermia rebels against the idea that she must conform to her father's wishes and reinforces this motif:
HERMIA: O hell! to choose love by another's eyes. (1.1.142)
Lysander and Hermia confide to Helena that they have decided to run off together to Lysander's aunt's house, which is beyond the Duke's' authority. Helena decides to use this information to show Demetrius that Hermia doesn't love him—that he can never marry her—and to win Demetrius back for herself.
Helena is left alone at the end of the scene, and in her monologue, she confesses that she's envious of Lysander and Hermia, jealous of Demetrius's love for Hermia (what does he see in Hermia that he doesn't see in her?), and feels that Demetrius made a mistake in preferring Hermia to her—but that she loves him anyway and wants him back.
She muses about the nature of love, and the effect that love can have on people in general, and on her in particular:
Love looks not with the eyes, but with the mind;
And therefore is wing'd Cupid painted blind.
Nor hath Love's mind of any judgment taste;
Wings and no eyes, figure unheedy haste. (1.1.239–242)
With this language, Helena explains that, when people fall in love—which they sometimes do at first sight (with "unheedy haste")—it affects their reasoning ability and their judgment. Love blinds them to everything except what they want to see in the other person, and their imagination runs away with them.
Later in the play, Shakespeare illustrates this "love is blind" theme very clearly. Titania has fallen hopelessly in love with Bottom. Bottom, who is not blinded by love and can see the situation as it is, wonders why Titania has fallen in love with him:
TITANIA: I pray thee, gentle mortal, sing again.
Mine ear is much enamored of thy note;
So is mine eye enthralled to thy shape;
And thy fair virtue's force perforce doth move me,
On the first view to say, to swear, I love thee.
BOTTOM: Methinks, mistress, you should have little reason
for that. And yet, to say the truth, reason and love keep
little company together now-a-days. (3.1.129–136)