Some scholars divide voluntary prayer into absolute and restricted; is it permissible to restrict oneself to the restricted without the absolute, or is all of it a recommended practice?

The questioner: Our Shaykh, may Allah bless you, some scholars divide voluntary prayer with regard to the ritual prayer into absolute and restricted. The restricted is: what is established from the Prophet (peace and blessings be upon him) by word or deed, such as the regular voluntary prayers, the Dhuha prayer, the prayer of ablution, the prayer for rain, and standing in night prayer. And the absolute is: that a person prays as much as he wishes, in pairs, at times other than those disliked, without making it a constant habit, so that it does not become a religious innovation, acting on the saying of the Prophet (peace and blessings be upon him) to the two companions who asked to accompany him in Paradise: . And some restrict themselves to the restricted voluntary prayer without the absolute. What is the correct view?

The Shaykh: And some?
The student: Restrict themselves to the restricted voluntary prayer without the absolute with regard to the ritual prayer?

The Shaykh: What is the evidence of this group?! Because it is completely clear that it contradicts some explicit texts regarding the absolute, provided it does not contradict other texts, such as praying at a time of dislike, for example. Among what comes to my mind now is the saying of him (peace and blessings be upon him): . So what is the evidence of those who restrict themselves to the restricted voluntary prayers? The scope for voluntary prayer in this hadith and similar ones is very wide. I think you remember with me the hadith in Abu Dawud—in my opinion—from the hadith of Abu al-Darda (may Allah be pleased with him), that the Prophet (peace and blessings be upon him and his family) said: . In a narration: . This is an absolute text. Does it have any voluntary prayer?! And as I say on such an occasion: this is a very important matter, that the Prophet (peace and blessings be upon him and his family) directed the Muslims to have a backup of voluntary prayers so that Allah (Mighty and Majestic) may complete for them the deficiency that may occur in their obligatory prayer, either in quantity or in quality. In quantity: one may lose one of the prayers due to being occupied with play, trade, children, family, and the like, and so on. This may happen to some people. As for quality: speak of it without harm, for many of those who pray are said to have prayed and not prayed, as he (peace be upon him) said in the hadith about the one who performed his prayer poorly, narrated in "Sahih al-Bukhari": . And the hadith is well known. So it is necessary for the Muslim to increase in voluntary prayer absolutely, whether it is restricted as mentioned in the question, or not restricted but absolute, as mentioned in the first hadith: . So the stronger position is: both, combining the absolute voluntary prayers and the restricted voluntary prayers. And there is no doubt that the restricted voluntary prayers are better, and indeed some of them may be obligatory, and among them, as we see: the eclipse prayer and the prayer of greeting the mosque, due to the command coming from the Prophet (peace and blessings be upon him and his family) regarding them.