Indeed, Stephen's speech in Acts 7 contains several problems, with four of these in verses 2-8 (including the two you mention). But
his usage is well within the parameters of acceptableness in the day. So, Longenecker (
EBC, in.loc., emphasis mine): <DIR><DIR>"There are a number of difficulties as to chronological sequence, historical numbers, and the use of biblical quotations in Stephen's address that have led to the most strenuous exercise of ingenuity on the part of commentators in their attempts to reconcile them. Four of these difficulties appear in vv. 2-8. Verse 3 quotes the words of God to Abraham given in Genesis 12:1 and implies by its juxtaposition with v. 2 that this message came to Abraham "while he was still in Mesopotamia, before he lived in Haran," whereas the context of Genesis 12:1 suggests that it came to him in Haran. Verse 4 says that he left Haran after the death of his father, whereas the chronological data of Genesis 11:26-12:4 suggests that Terah's death took place after Abraham's departure from Haran. Verse 5 uses the words of Deuteronomy 2:5 as a suitable description of Abraham's situation in Palestine, whereas their OT context relates to God's prohibition to Israel not to dwell in Mount Seir because it had been given to Esau. And v. 6 speaks of 400 years of slavery in Egypt, whereas Exodus 12:40 says 430. "We need not, however, get so disturbed over such things as, on the one hand, to pounce on them to disprove a "high view" of biblical inspiration or, on the other hand, to attempt to harmonize them so as to support such a view.
These matters relate to the conflations and inexactitude of popular Judaism, not necessarily to some then-existing scholastic tradition or to variant textual traditions.
In large measure they can be paralleled in other popular writings of the day, whether overtly Hellenistic or simply more nonconformist in the broadest sense of that term.
Philo, for example, also explained Abraham's departure from Ur of the Chaldees by reference to Genesis 12:1 (
De Abrahamo 62-67), even though he knew that Genesis 12:1-5 is in the context of leaving Haran (cf.
De Migratione Abrahami 176).
Josephus spoke of Abraham's being seventy-five years old when he left Chaldea (contra Gen 12:4, which says he was seventy-five when he left Haran) and of leaving Chaldea because God bade him go to Canaan, with evident allusion to Genesis 12:1 (cf.
Antiq. I, 154 [vii.1]). Likewise,
Philo also placed the departure of Abraham from Haran after his father's death (
De Migratione Abrahami 177). And undoubtedly the round figure of four hundred years for Israel's slavery in Egypt--a figure that stems from the statement credited to God in Genesis 15:13--was often used in popular expressions of religious piety in Late Judaism, as were also the transpositions of meaningful and usable phrases from one context to another.
