It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "Jibril (peace be upon him) said to me: (O Messenger of Allah,) the prayer has been made beloved to you, so take from it as much as you wish (in the form of voluntary prayers and lengthening them)."
The chain of this hadith contains a narrator named Ali bin Zayd bin Jud'an, who is da'if (weak) according to the majority of hadith scholars; however, the virtue of the prayer and the Prophet's (peace and blessings be upon him) fondness for it are established by other sahih narrations.
Hadith Referenceالمطالب العالية بزوائد المسانيد الثمانية / كتاب الصلاة / 219
Hadith Gradingمحدثین:إسناده ضعيف
Hadith Takhrij«حکم الحدیث المطالب العالیہ محققاً تنسیق د. سعد بن ناصر بن عبد العزيز الشَّثري- مکتبہ شاملہ :إسناده ضعيف. » «أخرجه مسند أحمد برقم: 2689، وأخرجه المعجم الكبير للطبراني برقم: 12929، وأخرجه إتحاف الخيرة المهرة بزوائد المسانيد العشرة برقم: 752/1»