All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
It has been reported that the optional prayer before the obligatory Thuhr prayer is 2 Raka'h. Ibn 'Umar narrated: "We observed and preserved from the Prophet
ten Raka'h (optional prayers): "2 before Thuhr, and 2 after it, 2 after Maghrib in his house, 2 after 'I'shaa' in his house, and 2 Raka'h before Fajr." [Al-Bukhari]
It is also reported that the Prophet stated that optional prayers before Thuhr are 4 Raka'h in the narration that you pointed to in your question and which was published in our website. Thus, both ways of performing optional prayers before Thuhr are confirmed, and there is no harm to comply with one of them. We think that it is more desirable for you to pray 4 Raka'h so that a house will be built for you in
. If you pray 3 Raka'h, you can either perform them with one Tashahhud, and one Salaam, or 2 Raka'h after which you say Salaam (end the prayer) [and these are called Shaf'] and then pray one Raka'h and say Salaam.
Nevertheless, there is no punishment for not praying optional prayers because they are not obligatory. However, the person who does not perform them is considered negligent and looses a big reward he would be most in need of on the Day of Judgment. In addition to this, the person who does not perform optional prayers is more likely to neglect obligatory prayers.
Allaah knows best.