Fasting just before Ramadaan:
The Messenger of Allaah (sallallaahu `alaihi wa sallam) said: “Do not precede Ramadaan by fasting a day or two before it, except for a man fasting his usual fast – let him fast it.”
Reported by Al-Bukhaaree (1914) and Muslim (1082) in their Saheehs.
The Messenger of Allaah (sallallaahu `alaihi wa sallam) said: “When only half of Sha`baan is left, do not fast.”
Authenticated by At-Tirmidhee (738), Ibn `Abdil-Barr (Al-Istidhkaar, 2/253) and Al-Albaanee (Sunan-ut-Tirmidhee,738).