Brihat Parashara Hora Shastra
षष्ठेऽब्दे पञ्चविंशाब्दे पितुर्मरणमादिशेत् । रन्ध्रजामित्रगे मन्दे मन्दाज्जामित्रगे रवौ ॥ २३॥
If Śani is in the 7th from Randhr Bhava, as Sūrya is in the 7th from Śani, the ages of 21, 26, or 30 will be fatal for the father.
english translation
SaSThe'bde paJcaviMzAbde piturmaraNamAdizet । randhrajAmitrage mande mandAjjAmitrage ravau ॥ 23॥
hk transliteration by Sanscript