It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "The niche grave (lahd) is for us, and the trench grave (shaqq) is for others than us."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6718