Al-Imam As-Suyutiyy said in his alfiyyah (Page 8):
«وَخُذْهُ حَيْثُ حَافِظٌ عَلَيْهِ نَصْ … وَمِنْ مُصَنَّفٍ بِجَمْعِهِ يُخَصْ»
which means: if you find a Hafidh explicit said so (“this hadith is sahih“) then take it from him, or a hafidh authored a book specific for it (in which he says “all the hadith in it are sahih“)
PDF LINK: https://archive.org/details/waq75686/page/n7/mode/2up