"That is what I told him."
Translation:C'est ce que je lui ai dit.
The indirect object pronoun, which is required here by the verb dire, is 'lui' (to him/her), which, unlike the direct object pronouns le/la (him/her), does not contract to l' before a vowel: "C'est ce que je lui ai dit"
I just have to say, as a detractor of redundancy, I loathe the 'it is it' construction in French.
Actually, with four words this phrase is even longer than you suggest.
A literal translation could be: It is it that. Or a case could be made for: That is that that. :-o
But it's just a formula, with one boilerplate meaning. The pronunciation is quick and easy, sess-kuh, like one punchy little word. I think it's actually a very elegant phrase.
C'est ce que