Why was Abu Talhah's Islam accepted but Muhajir Umm Qais's Hijrah not, even though the motive for the act of worship (Islam and Hijrah) was for the sake of marriage in both cases?

The difference between the emigration (Hijra) of Abu Talha and that of Umm Qays is that Abu Talha embraced Islam out of a desire for it, and to this desire, he added the desire to marry Umm Sulaym. The proof of this is that he later perfected his Islam. As for the emigrant of Umm Qays, he only emigrated with the intention of marrying. Thus, his act came in the form of an action without the intention of worship. His action is not forbidden, nor is his marriage invalid. For emigration is not pure worship; rather, it depends on the emigrant's intention. So, whoever emigrates for a permissible trade, his emigration is permissible. Whoever emigrates for an act of proximity to God, his emigration is an act of obedience. Whoever emigrates for a forbidden purpose, his emigration is forbidden. If he mixes in his emigration the intention of the permissible with the intention of proximity and obedience, then it is judged according to what dominates his intention and purpose.