Mahārāja Parīkṣit, now your duration of life is limited to seven more days, so during this time you can perform all those rituals which are needed for the best purpose of your next life.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
तवाप्येतर्हि कौरव्य सप्ताहं जीवितावधिः । उपकल्पय तत्सर्वं तावद्यत्साम्परायिकम्
tavāpyetarhi kauravya saptāhaṃ jīvitāvadhiḥ | upakalpaya tatsarvaṃ tāvadyatsāmparāyikam
SB 2.1.14