crosswise, he should use it crosswise, since no clear sunnah has been established regarding this.
“Beginning with the right side of his mouth, …”
His statement, “beginning with the right side of his mouth,” is supported by the fact that the Prophet, peace and blessings be upon him, “liked to begin with the right in putting on his sandals, combing his hair, purifying himself, and in all his affairs” (1).
The scholars differed as to whether one should use the tooth-stick with the right hand or the left hand (2).
Some said: with the right hand, because using the tooth-stick is a sunnah, and the sunnah is an act of obedience and a means of drawing near to Allah Most High. It should therefore not be done with the left hand, since the left is reserved for removing filth, based on the principle that the left hand is used for filth and the right for everything else.
Since it is an act of worship, it is preferable to perform it with the right hand.
Others said that the left hand is preferable, and this is the well-known position of the madhhab, because it is used to remove what is unpleasant, and removing such things is done with the left hand, as in cleansing oneself after relieving oneself and using stones for that purpose.
Some Mālikīs made a distinction: if one uses the tooth-stick to cleanse the mouth—as when waking from sleep, or to remove the effects of eating and drinking—then he should use the left hand, because this is the removal of what is unpleasant (3).
But if he uses the tooth-stick in order to attain the sunnah, then he should use the right hand, because it is purely an act of devotion. For example, if he performs ablution and uses the tooth-stick at the time of ablution, then shortly afterward comes to the prayer, he uses the tooth-stick in order to attain the sunnah.