A man said to Abdullah bin Umar, "Will you not go out to fight?"He replied, "I heard the Messenger of Allah ﷺ say, 'Islam is built upon five: bearing witness that there is no god but Allah and that Muhammad is the Messenger of Allah, establishing the prayer, giving the zakat, fasting Ramadan, and pilgrimage to the House.'"
حدثنا ابن نمير حدثنا حنظلة سمعت عكرمة بن خالد
إن رجلا قال لعبد الله بن عمر ألا تغزو قال إني سمعت رسول الله ﷺ يقول إن الإسلام بني على خمس شهادة أن لا إله إلا الله وأن محمدا رسول الله وإقام الصلاة وإيتاء الزكاة وصيام رمضان وحج البيت
Its isnad is sahih. Hanzala is Ibn Abu Sufyan bin Abdul-Rahman Jumahi Makki. Ikrima is Ibn Khalid bin Aas Makhzumi. Muslim narrated the hadith at 1:20 through Ibn Numayr with this same isnad. Bukhari narrated it at 1:46-47 from Ubaydullah bin Musa from Hanzala bin Abu Sufyan, but limited to the raised portion only, without mentioning the question at its beginning, and Hafiz pointed out in Fath al-Bari that this matches Muslim's version of this narration. Its meaning has already passed in fuller form with a different wording and a different, daif isnad at 5672, and we noted this there. The raised portion of it has also already passed through the narration of Asim from his father from Ibn Umar, so see 4798.Regarding the wording "the testimony that there is no god but Allah," this is how it is established in K and M here, with the second testimony, "and that Muhammad is the Messenger of Allah," omitted. This matches Muslim's version of it from this same route. It is certainly intended by implication, and by the indication of the other narrations. It was added at this point in H, and I believe this addition came from the printer or the copyist, since it contradicts what is established in the two manuscript originals and in Sahih Muslim. Nawawi discussed this in his commentary on Sahih Muslim, 1:177-179, saying, As for his limiting himself in the fourth narration to only one of the two testimonies, this is either a shortcoming on the part of the narrator in omitting the other testimony that other memorizers established, or else the narration originally occurred this way, with the omission being a matter of relying on one of the two paired items to indicate the other, omitted one.A note. In the printed copy of Nawawi's text, the phrase appeared as "one of the two paired items," which is a mistake and a corruption by the copyist or the printer. And what would "the two paired items" even mean here? The context clearly shows the printed version to be in error.