Is it permissible to refrain from childbearing due to cramped living conditions and the husband's illness?

A husband is not permitted to prevent his wife from conceiving, because Islam has encouraged procreation, and Allah has guaranteed sustenance, as He said: {And there is no creature on earth but that upon Allah is its provision, and He knows its place of dwelling and resting. All is in a clear register.} Regulating childbirth is permissible when there is a need for it, provided that both spouses agree.