to rise early in the morning, get up at daybreak to act
This verb pictures someone getting up at first light to set about something. Its background image is practical and physical: a traveler loading the back of a donkey or camel before dawn so the group can break camp and move out. From that scene the word came to mean simply to start the day early, to be up and doing before the sun is high.
In most of its appearances it keeps that plain, literal force. Narratives use it again and again to launch a scene: a person rises early in the morning and then journeys, builds an altar, sets out for battle, or goes to look at something. The early hour signals purpose and readiness, not merely the time of day.
From this literal use the word also grew a settled figure of speech. Hebrew often pairs it with a second verb (speaking, sending, warning) to say that the action was done early and therefore eagerly, persistently, and untiringly. The prophets, above all Jeremiah, use this pairing to describe how God kept speaking and sending messengers over and over, refusing to give up. Here rising early is no longer about the clock; it is about earnest, repeated, wholehearted effort.