Yahya bin Yamar reported,
Someone said to Ibn Umar, "We have men among us who claim that the matter is in their own hands, so if they wish they may act, and if they wish they may not act."Ibn Umar replied, "Tell them that I disown them and that they have nothing to do with me."Then he said, Jibreel ﷺ came to the Prophet ﷺ and asked, "Muhammad, what is Islam?"The Prophet ﷺ answered, "That you worship Allah, associating nothing with Him, that you establish the prayer, pay zakat, fast Ramadan, and make the pilgrimage to the House."Jibreel asked, "So if I do that, am I a Muslim?"He said, "Yes."Jibreel said, "You have spoken the truth."Then he asked, "What is doing good?"The Prophet ﷺ answered, "That you stand in awe of Allah Most High as though you see Him, for even if you do not see Him, He surely sees you."Jibreel asked, "So if I do that, am I one who does good?"He said, "Yes."Jibreel said, "You have spoken the truth."Then he asked, "What is faith?"The Prophet ﷺ answered, "That you believe in Allah, His angels, His books, His messengers, the resurrection after death, the Garden, the Fire, and in destiny, all of it."Jibreel asked, "So if I do that, am I a believer?"He said, "Yes."Jibreel said, "You have spoken the truth."Ibn Umar added that Jibreel 
used to come to the Prophet ﷺ in the form of Dihya.
Ahmad 5857
Sahihحدثنا عفان حدثنا حماد بن سلمة عن إسحاق بن سويد عن يحيى بن يعمر عن ابن عمر عن النبي ﷺ بمثله قال وكان جبريل عليه السلام يأتي النبي ﷺ في صورة دحية
Its isnad is sahih. Ishaq bin Suwayd bin Hubayra Adawi is a trustworthy successor (tabii thiqah) who narrated from Ibn Umar and Ibn Zubayr, but here he narrated from Yahya bin Yamar from Ibn Umar. Ahmad, Ibn Saad, and others rated him trustworthy, and Bukhari gave his biography in al-Kabir 1/1/389.This hadith is a longer version of the one before it. Ibn Saad narrated the last part of it in 4/1/184 from Affan bin Muslim, Ahmad's teacher here, with this same isnad. The Hafiz mentioned it in al-Isabah in the biography of Dihyah, 2:161,162, and attributed it to Nasai with a sahih isnad, but I did not find it in Sunan Nasai from the hadith of Ibn Umar. Rather, it appears there at 2:266,267 from the hadith of Abu Hurairah. So perhaps this hadith of Ibn Umar is in Sunan al-Kubra.Dihyah is spelled with a kasrah on the dal and a sakin on the ha (both being non-guttural letters), though a fathah on the dal is also permissible.A note, a printing error occurred in the copy of al-Isabah regarding this hadith, giving it as "from Yahya bin Muammar from Abu Umar," when the correct version is "from Yahya bin Yamar from Ibn Umar." So its correction can be drawn from here.