Shaykh Wasiullah Allahabadi (Allah have mercy on him) said,

For islah (spiritual improvement, reformation, betterment) two things are essential.

One of them is instructions (ta’leem) and the other is training (tarbiyet).

The instructions are what you people do by this learning from books (lectures, etc.) from me. However, only instructions are not sufficient (for islah). They must be accompanied with training and spiritual cleansing (tazkia). It is for this that I bother you people and ask questions, admonish and catechize. This is the tazkia and tarbiyet’ (to acertain practical application of instructions given for successful achievement of islah).

Halaat e Muslih al-Ummat ra, volume 2, page 23