Valmiki Ramayana Yuddha Kanda Sarga 17 Shloka 54
Original Shlokaऋतेनियोगात्सामर्थ्यमवबोद्धुंनशक्यते । सहसाविनियोगोहिदोषवान्प्रतिभातिमे ।।6.17.54।।
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नियोगात् ऋते: only when entrusted with duty, सामर्थ्यम् capability, अवबोद्धुम् will be known, नशक्यते: not possible, सहसा: inconsiderately, विनियोगः appointment to a duty, दोषवान् will be faulty, मे: to me, प्रतिभाति: to understand.
"When entrusted with duty one's capability will be known. It is not possible to appoint him for duty inconsiderately without understanding (his capacity) as it will be faulty."