In Jayadeva's Gita Govinda Radha, finding Krishna dancing with others in spring, withdraws in jealous grief until her friend carries messages between them and Krishna, repentant, begs her to set her foot on his head; the devotional legend says Jayadeva dared not write that line and Krishna came and wrote it himself.
Spring in the woods by the Yamuna. Radha waits, and her friend tells her Krishna is dancing with the other cowherd women. Radha goes away hurt and will not come; Krishna, left alone, remembers her and is sorry. The friend goes between them, describing to each the other's longing. At last Krishna comes to Radha, and when she turns from him he begs, and asks her to set her tender foot on his head; she relents, and the poem ends in their union.
The legend of the line (Puri and Gaudiya tradition)
East India · PuriVaishnava
Devotees tell that when Jayadeva reached the verse in which Krishna asks Radha to set her foot on his head, he could not bring himself to write that God would say it. He put down the leaf and went to bathe. Krishna came in Jayadeva's form, wrote the line, and ate the meal his wife Padmavati had cooked; when the poet returned he found the verse written and knew who had been there.
Sources: Edwin Arnold, The Indian Song of Songs (1875), in Indian Poetry (Project Gutenberg 25965); Jayadeva (Encyclopaedia Britannica); Gita Govinda (Wikipedia); Who Will Understand This (Sri Chaitanya Saraswat Math); Jayadeva (Wikipedia)