Tasawwuf and the Completion of Deen
The historical background of Hadith-e-Jibreel further adds to the significance of this Hadith. Jibreel (AS) came in human form at a time when the Holy Prophet ﷺ had returned from the Last Hajj. Hence, this event took place in the last portion of the Holy Prophet's ﷺ life. Deen-e-Islam had been completed at that time and all the commandments had been sent down. In other words, the crux of the Deen was stated by Hazrat Jibreel (AS) and the Holy Prophetﷺ said: "He had come to teach you your Deen".
The commandments of Deen were consolidated and its summary was presented before the Holy Prophetﷺ. Hence, Deen consists of three factors. For instance, there are three Rakats in the Maghrib prayer. If someone says two Rakats and skips the thrid one, his prayer will not be performed. Similarly, when a person leaves Tasawwuf, he leaves one-third of Deen, Obviously, the completion of Deen does not take place in this case.
Maulana Allah Yar Khan (RA)--Dalail-us-Salook