Musnad Ahmad 2145

It was narrated from 'Abdullah bin 'Abbas (رضي الله عنه) that a man came to the Prophet (ﷺ) and said: O Prophet (ﷺ) of Allah, I am an old man, I am sick and it is difficult for me to stand. Tell me of a night that Allah may make coincide with Lailatal-Qadr. He said: “You should [strive to pray] on the seventh night.”