It is narrated from Sayyiduna Abu Umamah al-Bahili (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever walks to an obligatory prayer in a state of purity, his reward is like the reward of a pilgrim in ihram for Hajj; and whoever walks to the glorification of the forenoon (the Duha prayer), his reward is like the reward of one performing Umrah."
"And a prayer following another prayer, with no idle talk between them, is recorded in Illiyyin."
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7703