Hadithcore
Al-Adab Al-Mufrad, 336
sahih· Al-Albani

Zayd ibn Aslam reported that his father heard 'Umar state, "Praise is slaughter." The transmitter added, "He meant when it is accepted."

حَدَّثَنَا مُحَمَّدٍ، قَالَ‏:‏ حَدَّثَنَا عَبْدُ السَّلامِ، قَالَ‏:‏ حَدَّثَنَا حَفْصٌ، عَنْ عُبَيْدِ اللهِ، عَنْ زَيْدِ بْنِ أَسْلَمَ، عَنْ أَبِيهِ قَالَ‏:‏ سَمِعْتُ عُمَرَ يَقُولُ‏:‏ الْمَدْحُ ذَبْحٌ، قَالَ مُحَمَّدٌ‏:‏ يَعْنِي إِذَا قَبِلَهَا‏.‏

References2 variants
In-Book Reference
Book 16, Hadith 4
English Reference
Book 16, Hadith 336