Fiqh-us-Sunnah Volume 1, Purification and Prayer, Fiqh 1.035.

Section : Nullification of ablution.

It is not desirable that one who is making ablution should leave any of the sunan that have just been mentioned. The person would then lose the great reward of these (simple)acts. Anytime one abandons the sunnah, he has done a disliked deed.