Hilchos Ishus 5:29
Let’s say that a man consecrates a woman by giving her a cup. If it is filled with water, then marriage depends on the value of the cup plus its contents. If it is filled with wine, then marriage depends on the value of the cup alone, without its contents. If it is filled with oil, then marriage depends on the value of the contents without the cup. Therefore, if the oil was worth less than a prutah, it is doubtful whether marriage was effected or not. If the oil is worth a prutah or more, then marriage has definitely been effected regardless of the cup’s value.
Hilchos Ishus 6:1
Let’s say that a man consecrates a woman on a condition. If that condition is met, then marriage is effected; if not, then the kiddushin he gave her is immaterial. This is so regardless of whether the condition was made by the man or the woman. Every condition stated in matters of marriage, divorce, financial transactions and other areas of business must adhere to four criteria, which will be addressed in the next halacha.