Jesus commands the healed leper not to tell anyone about the miracle to avoid already drawing too much attention to himself, as he did on several occasions during his ministry (Matthew 9:30, Matthew 12:16, Matthew 17:9; Mark 5:43, Mark 7:36, Mark 8:26). He may have wanted to avoid having too many seeking his healing all at the same time (see Luke 5:15–16; John 6:26–27), and he definitely wanted to avoid being crowned as an earthly king (see Matthew 9:30, Matthew 12:16, Matthew 17:9).
The reason Jesus commands the leper not to tell anyone of the miracle healing is probably because he did not want to draw too much attention to himself at the time. He did so on more than a few occasions during his ministry (Matthew 9:30, Matthew 12:16, Matthew 17:9, Mark 5:43, Mark 7:36, Mark 8:26). It is quite possible that he wanted to avoid a type of situation in which masses of people simultaneously approach him for healing (see also Luke 5:15 and John 6:26). Regardless, he most certainly wanted to avoid creating the impression that he came in order to rule as king on earth (see also Matthew 9:30, Matthew 12:16, Matthew 17:9).1
4 Puis Jésus lui dit: Garde-toi d'en parler à personne; mais va te montrer au sacrificateur, et présente l'offrande que Moïse a prescrite, afin que cela leur serve de témoignage.