आ॑स्ते भ॑ग आ॑सीनस्य।
च॑राति च॑रतो भ॑गः॥
(Note that the ऐतरेयब्रा॑ह्मण unfortunately doesn't preserve the Vedic accents. I restored them myself here.)
Translation: "The fortune of the sitter sits; of the stander stands up; of him who lies down, lies; the fortune of the mover shall move. Thus, move!"
Word-by-word: आ॑स्ते < आस् "sit", भ॑गस् < भ॑ग "fortune", आ॑सीनस्य < आ॑सीन < आस् "sit", ऊर्ध्व॑स् < ऊर्ध्व॑ "up", तिष्ठति < स्था "stand", ति॑ष्ठतस् < ति॑ष्ठन् < स्था "stand", शे॑ते < शी "lie", निप॑द्यमानस्य < निप॑द्यमान < नि॑ पद् "lie down", च॑राति < चर् "move", च॑रतस् < च॑रन् < चर् "move", भ॑गस् < भ॑ग "fortune", च॑र < चर् "move", एव॑ "thus", इ॑ति.
Context: In this episode of the ऐतरेयब्रा॑ह्मण, the king ह॑रिश्चन्द्र ऐक्ष्वाक॑ promised व॑रुण that he would sacrifice his son रो॑हित to Him. (Contrary to modern Hindus' views, human sacrifice was clearly a literal practice in Vedic times.) However, ह॑रिश्चन्द्र kept postponing the sacrifice until रो॑हित grew up, and when he finally asked रो॑हित to be sacrificed, रो॑हित refused and fled into the forest.
रो॑हित continued to wander until he heard that व॑रुण had caused his father to become ill. But when he tried to visit his father, इ॑न्द्र kept coming to him every year in the disguise of a ब्राह्मण॑, telling him to continue wandering for another year. This verse was told by इ॑न्द्र to रो॑हित after the third year, telling him to wander for a fourth, since moving brings fortune.
Why I like this verse: It depicts the action-centered view of the Vedic religion, in which you controls your own fate through your free will. If you live a life of inaction (metaphorically sitting or lying down), nothing good will happen to you; but your fortune will rise and move only when you yourself rise and move.