Can Husband Suck Wife's Breasts?
Question

Is it permissible for a man to suck on his wife’s breasts during intercourse?
Praise be to Allah.Husband-Wife sexual relation: Do and Don’ts 
The husband may enjoy intimacy with his wife in whatever way he wishes; the only thing that is forbidden is anal intercourse and intercourse during the wife’s menstrual period or nifas (post-partum bleeding). Apart from that, he may enjoy his wife in whatever way he wants, such as kissing, touching, looking, etc. 
Sucking wife’ breasts: Permissible? 
Even if he sucks on her nipples, this comes under the heading of the intimacy that is permissible, and it cannot be said that the milk has any effect on him , because if an adult breastfeeds, it does not have any effect of making him a mahram. Rather the breastfeeding that has this effect is that which takes place during the first two years of life. 
The scholars of the Standing Committee said: 
“It is permissible for a husband to enjoy all of his wife’s body, apart from the back passage and intercourse during the wife’s menstrual period or nifas (postpartum bleeding), or when in ihram for Hajj or ‘Umrah, until he has exited ihram completely.” (Shaykh ‘Abd al-‘Aziz ibn Baz, Shaykh ‘Abd-Allah ibn Qa’ud, Fatawa al-Lajnah al-Daimah, 19/351, 352)  
The scholars of the Standing Committee said:  
“It is permissible for the husband to suck his wife’s breasts, and if any milk reaches his stomach it does not have the effect of making him a mahram.” (Shaykh ‘Abd al-‘Aziz ibn Baz, Shaykh ‘Abd al-Razzaq ‘Afifi, Shaykh ‘Abd-Allah al-Ghadyyan, Shaykh ‘Abd-Allah ibn Qa’ud) 
Shaykh Muhammad ibn Salih al-‘Uthaymin said: 
“Breastfeeding by an adult does not have the effect of making him a mahram, because the breastfeeding that has that effect is five breastfeedings or more within the first two years of life before weaning. Breastfeeding by an adult does not have that effect. Based on this, if we assume that someone breastfed from his wife or drank her milk, he cannot become a son to her.” (Fatawa Islamiyyah, 3/338)
Can a husband touch wife’s private parts?
With regard to it being permissible to enjoy anything concerning which there is no prohibition, there follow some of the views of the scholars: 
Ibn Qudamah said: 
“There is nothing wrong with enjoying the area between the buttocks without any penetration, because what is forbidden is the back passage , which is mentioned specifically, which is forbidden because of the filth, and that is specific to the back passage, therefore it is expressly forbidden.” (Al-Mughni, 7/226)
Al-Kasani said: 
“Among the sahih rulings on marriage is that it is permissible to look at and touch every part of her from head to foot when she is alive, because intercourse goes beyond looking and touching, so it is more appropriate that touching and looking should be permitted.” (Badai' al-Sanai’, 2/231)
Ibn ‘Abidin said: 
“Abu Yusuf asked Abu Hanifah about a man who touches his wife’s private part and she touches his to stimulate arousal – did he see anything wrong with that? He said: No, and I hope that the reward will be greater.” (Radd al-Muhtar, 6/367)
The Prophet (peace and blessings of Allah be upon him) stated that this is permissible when he forbade intercourse in the vagina with a menstruating woman , but he permitted all other parts of her body. So it is more obvious that it is permissible at times other than menstruation. 
Shaykh Muhammad ibn Salih al-‘Uthaymin (may Allaah have mercy on him) said: 
“The words “He may enjoy everything else of her apart from that” means that the man may enjoy every part of the menstruating woman apart from the vagina. 
It is permissible to enjoy what is above and below the waist wrapper (izar), but the woman should be wrapped in a waist wrapper, because the Prophet (peace and blessings of Allah be upon him) used to tell ‘Aishah to wrap herself in a waist-wrapper when she was menstruating, then he would be intimate with her. He told her to do that lest he saw something that he disliked, namely the menstrual blood. But if the husband wants to enjoy the area between the thighs, for example, there is nothing wrong with that. 
If it is said: What do you say about the words of the Prophet (peace and blessings of Allah be upon him) when he was asked what part of his wife is permissible for a man when she is menstruating and he said, “You have that which is above the waist-wrapper” and this indicates that one may only enjoy that which is above the waist-wrapper?  
The answer is as follows: 

That is in order to be on the safe side and to avoid that which is forbidden.
It may vary according to circumstances. The words of the Prophet (peace and blessings of Allah be upon him), “Do everything apart from intercourse” may be taken as being addressed to one who can control himself, and the words, “You have that which is above the waist-wrapper” may be taken as being addressed to one who cannot control himself, either because his religious commitment is too weak or his desire is too strong.” (Al-Sharh al-Mumti’, 1/417) 

And Allah knows best.