Abu Hurairah (May Allah be pleased with him) reported:
The Messenger of Allah (ﷺ) said, "Any matter of importance which is not begun with Al-hamdu lillah (praise be to Allah) remains defective."[Abu Dawud]. (PT)
App reference (PT): Book 14, Hadith 2 (PT)
Arabic/English book reference (PT): Book 14, Hadith 1394 (PT)