Is it a Saheeh Hadeeth where the Prophet, sallallaahu ‘alayhi wa sallam, advised us to do our utmost for our worldly life as if we will live forever, and to increase our good acts to be ready for the Hereafter as if we will die tomorrow? May Allaah reward you.

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

Al-Bayhaqi and Ad-Daylami reported this narration, but it can not be attributed to the Prophet, sallallaahu ‘alayhi wa sallam, because he, sallallaahu ‘alayhi wa sallam, did not say it. As-Suyooti classified this Hadeeth as Dha‘eef.

On the other hand Al-Haytham stated that it was ‘Abdullaah Ibn ‘Amr Ibn Al-‘Aas who said these words.

Allaah Knows best.