Brihat Parashara Hora Shastra
चतुर्विंशतिवर्षाणि यावद् गच्छन्ति जन्मतः। जन्मारिष्टं तु तावत् स्यादायुर्दायुं न चिन्तयेत्॥ २॥
Evils, causing premature end, exist up to the 24th year of one‟s age. As such, no definite calculation of life span should be made till such year of age.
english translation
caturviMzativarSANi yAvad gacchanti janmataH। janmAriSTaM tu tAvat syAdAyurdAyuM na cintayet॥ 2॥
hk transliteration by Sanscript