It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Supplication is the essence of worship."
No one narrated this hadith from Aban (may Allah have mercy on him) except Ubaydullah (may Allah have mercy on him), and Ibn Lahi'ah (may Allah have mercy on him) is alone in narrating it.
Hadith Referenceالمعجم الأوسط / باب الباء / 3196
Hadith Takhrij«أخرجه الترمذي فى «جامعه» برقم: 3371»