I heard the Messenger of Allah ﷺ entering the state of ihram, his hair matted with gum, saying, "Here I am, O Allah, here I am. Here I am, You have no partner, here I am. Truly all praise, favor, and dominion belong to You. You have no partner."He said, I also heard Umar bin Khattab entering ihram with the same words as the Messenger of Allah ﷺ, adding to them, "Here I am at Your service, and ready to obey You. All good is in Your hands. To You we turn in longing, and to You belongs the deed."
حدثنا يعقوب حدثني ابن أخي ابن شهاب عن عمه قال أخبرني سالم بن عبد الله بن عمر
سمعت رسول الله ﷺ يهل وهو ملبد يقول لبيك اللهم لبيك لبيك لا شريك لك لبيك إن الحمد والنعمة لك والملك لا شريك لك قال و سمعت عمر بن الخطاب يهل بإهلال رسول الله ﷺ ويزيد فيها لبيك وسعديك والخير في يديك والرغباء إليك والعمل
Its isnad is sahih. Muslim narrated it, 1:329-330, through the narration of Yunus from Zuhri from Salim, at greater length than this, and it states, as here, that the addition at the end of the talbiyah is from Umar bin Khattab.The hadith of the talbiyah has already appeared several times, without this addition, at 4821, 4895, 4896, 4997, 5019, 5024, 5086, 5954, 5508, 6021. It has also appeared through the narration of Bakr bin Abdullah Muzani from Ibn Umar at 4227, and through the narration of Nafi from Ibn Umar at 5071 and 5475, attributing this addition to Ibn Umar, not to Umar.Hafiz noted in Fath al-Bari, 3:325, that Muslim alone narrated this addition, apart from Bukhari, and he said, "This much is also found in Malik's narration, with him [i.e. with Muslim], from Nafi from Ibn Umar, that he used to add to it," and he mentioned something similar, so it became known that Ibn Umar followed his father's example in that.Malik's narration from Nafi is found in Muwatta, 1:307, 308.The reconciliation that Hafiz made between the two narrations of Salim and Nafi is correct, because Nafi only related what he heard from Ibn Umar regarding the wording of the talbiyah, both the original and the addition, and his narration does not state that Ibn Umar told him that this addition was from himself. As for Salim's narration here and in Sahih Muslim, it clearly states that his father told him that Umar used to add these words after the talbiyah which he had heard from the Messenger of Allah ﷺ.As for confirming the poetry, its meaning has already appeared in a longer hadith at 6027.