Exodus 34:1 (KJV) And the LORD said unto Moses, Hew thee two tables of stone like unto the first: and I will write upon these tables the words that were in the first tables, which thou brakest.
God said he would write on the tables of stone. Later in the chapter we see Moses writing on the tables of stone:
Exodus 34:28 (KJV) And he was there with the LORD forty days and forty nights; he did neither eat bread, nor drink water. And he wrote upon the tables the words of the covenant, the ten commandments.
God said he would write but Moses did the writing. Does that mean God lied? No. God wrote using Moses. All scripture was written by God using human instruments.