Invite (all) to the way of thy Lord with wisdom and beautiful preaching; and argue with them in ways that are best and most gracious: for thy Lord knoweth, best who have strayed from His Path, and who receive guidance. (Qur'an 16:125)
Qur’an mentions in Surah Baqarah chapter 2 verse 221
“Do not marry unbelieving women until they believe: a slave woman who believes is better than an unbelieving woman even though she allure you. Nor Marry (your girls) to unbelievers until they believe: a man slave who believes is better than an unbeliever even though he allure you. Unbelievers do (but) beckon you to the Fire. But Allah beckons by His Grace to the Garden (of Bliss) and forgiveness, and makes His signs clear to mankind: that they may receive admonition”.
2.This life is a test for Here-after:
According to the Qur’an in Surah Mulk chapter 67 verse 2
“He Who created Death and Life, that He may try which of you is best in deed,
and He is the Exalted in Might, Oft-Forgiving”.
3.Concept of Salvation cannot differ amongst Life-Partners:
The ultimate goal and salvation for every muslim is to attain paradise in the Hereafter. A true husband or a wife will also want his/her spouse to attain paradise in the here-after. How can two life-partners live together if their ultimate goal i.e. Salvation differs? Or if the ways that they have chosen to lead to this goal are different? Such a marriage would be like a vehicle whose one tyre is that of a cycle while the other tyre is that of a truck. How will the vehicle run smoothly? Similarly if the beliefs or conceptsof salvation of the spouses differ then how can they live in congruence and achieve marital harmony?