We read in Parashat Chayei-Sara of Avraham’s strict instruction to his servant to choose as a wife for Avraham’s son, Yitzchak, a woman from Avraham’s birthplace, and not from the Canaanite tribes among whom they lived (24:3-4). The Ramban, commenting later in this parasha (25:6), notes the irony in the fact that Avraham himself, after the death of his wife, Sara, married another woman – Ketura – who does not appear to have been from his homeland. The Torah (25:1) gives no information about Ketura, but there is no indication that she originated from Aram Naharayim, as Avraham had insisted that his daughter-in-law must. Curiously, Avraham demanded that his servant bring for Yitzchak a wife from Aram Naharayim – going so far as to make the servant take an oath to this effect – but he did not insist on this policy for himself. (The Ramban presumes that Ketura was a Canaanite, but also entertains the possibility that she was Egyptian or Philistine.)
The Ramban answers, somewhat ambiguously, that this policy was relevant only to Yitzchak “ki alav nikhrat ha-berit” – the covenant with God was made only for him. Meaning, God’s special covenant with Avraham’s offspring applied only to Yitzchak and his progeny, as God indicated earlier in Sefer Bereishit (“ki be-Yitzchak yikarei lekha zara” – 21:12). It seems that only those descendants included in the covenant could not be produced from a Canaanite woman; it made no difference to Avraham if he begot other children with a woman from Canaan. The Ramban does not, however, explain why this is the case.
One simple explanation that has been suggested is based upon Chizkuni’s understanding of Avraham’s insistence that Yitzchak not marry a Canaanite woman. Chizkuni writes (24:3) that this stemmed from Avraham’s concern that people might attribute his descendants’ claim to the land of Canaan to family connections. If Yitzchak had married a Canaanite woman, people might assume that Yitzchak received rights to the land as a gift from his wife’s family. Avraham insisted on making it clear that his descendants’ rights to the Land of Israel originate from God’s promise, and not from a familial connection, and so he demanded that his servant bring Yitzchak a wife from a distant land. If so, it has been suggested, then we can perhaps readily understand why Avraham had no qualms about marrying a Canaanite woman as an older man. The concern was relevant only with respect to Yitzchak’s hold on the Land of Israel, and so once this has been affirmed through Yitzchak’s marriage to a woman from Aram, Avraham did not have any concerns about marrying a woman from Canaan.