It is not a Condition that the One Who delivers Sermon on Friday should be the Imam
Question :
Is it a condition that the one who delivers the sermon on Friday be the Imam?
Answer:
The majority of the scholars hold that it is not a condition that the Khatib be the Imam who leads them in prayer, because nothing has been reported to this effect. The Malikis disagree on this, saying that it is a condition that the one who gives the sermon on Friday be the one who leads them in prayer, basing their argument on the fact that the sermon is inextricably linked to the prayer and therefore, it is not permissible to divide them between two Imams without a valid excuse. And through Allah is attained success.
Source:
The Permanent Committee
Fatawa Islamiyah, Vol. 2 Pages 443-444