Musnad Ahmad 430:10

Yazid ibn Harun narrated to us, he said: Hammad ibn Salamah informed us, from Yazid al-Raqashi, from Abu Na'amah, that Abdullah ibn Mughaffal heard a son of his saying: "O Allah, I ask You for al-Firdaws and such and such, and I ask You for such and such." He said: "O my son, ask Allah for Paradise and seek refuge in Allah from the Fire, for I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: 'There will be in this nation people who will transgress in supplication and in purification.'"