The Prophet ﷺ said, "Seek out Laylat al-Qadr in the last ten remaining nights, in the last nine remaining nights."
حدثنا عبد الرزاق حدثنا معمر عن الزهري عن سالم
أن النبي ﷺ قال التمسوا ليلة القدر في العشر الغوابر في التسع الغوابر
Its chain of transmission is sahih. "Ghawabir" here means "the remaining ones," though in another context it can mean "the past." Ibn Manzur says in Lisan Arab, "Ghabara al-shay yaghburu ghuburan" means it remained and departed. And "ghabara al-shay yaghburu" means it remained. "Al-ghabir" means the remaining, and "al-ghabir" means the past. It is one of those words that carries opposite meanings.See numbers 4499, 4547, 4671, 4808, and 6474.