Valmiki Ramayana Ayodhya Kanda Sarga 105 Shloka 25
Original Shlokaहृष्यन्त्यृतुमुखं दृष्ट्वा नवं नवमिहागतम्। ऋतूनां परिवर्तेन प्राणिनां प्राणसङ्क्षयः।।2.105.25।।
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ऋतुमुखम् setting of a season, दृष्ट्वा having seen, इह now, नवं नवम् something new (flowers and fruits), आगतम् have arrived, हृष्यन्ति feel delighted, ऋतूनाम् of seasons, परिवर्तेन by changes, प्राणिनाम् of living beings', प्राणसङ्क्षयः life span decreases.
At the advent of each new season men feel delighted to see the newly blossomed flowers and fruits. But with the change of the scasons the life span also diminishes.