once
وَقَالَ صلى الله عليه وسلم: ((لاَ تَجْعَلُوا قَبْرِي عِيداً وَصَلُّوا عَلَيَّ؛ فَإِنَّ صَلاَتَكُم تَبْلُغُنِي حَيْثُ كُنْتُمْ)).
Meaning
He (PBUH) also said: ‘Do not take my grave as a place of habitual ceremony. Send prayers upon me, for verily your prayers reach me wherever you are.
Source and references
Hisn al-Muslim, entry 220.The reference is copied from the edition; separate editorial verification is not complete yet.
Source edition: Fortress of the Muslim. Open source ↗