Imam ‘Ali ibn al-Husayn Zayn al-’Abidin (‘a) used to gather all his companions at the beginning of Sha’ban and say to them, “O my companions, do you know what this month is? It is Sha’ban. The Holy Prophet (S) used to say, ‘Sha’ban is my month.’ You should thus fast during this month as a sign of your love for your Prophet (S) and as a sign of seeking nearness to your Lord. I swear by Him Who grasps my soul in His Hand that I heard my father Husayn (‘a), saying that he heard Imam ‘Ali, the Commander of the Faithful (‘a), saying: ‘Any one who fasts during Sha’ban for the love of the Messenger of Allah (S) to seek nearness to Almighty Allah, Almighty Allah will love him,and draw him nearer to Himself on the Day of Resurrection and definitely reward him with Paradise.
— Imam Sadiq (a), Mafatih al-Jinan, pp. 154.