Muqatil bin Hayyan (may Allah have mercy on him) said: "But do not make promises to them secretly" [Surah al-Baqarah: 235] means obscene speech, that is, the man should not address her with hints of intercourse from himself; and others say that it means zina.
(b) Al-Hasan (may Allah have mercy on him) said regarding hinting at marriage: he sends word to her during her waiting period, saying: "I am desirous of you, I am eager for you, and I wanted to let you know; when your waiting period is over, you may decide as you see fit." Ata (may Allah have mercy on him) said: He hints and does not declare it openly. He says: "I have a need, so be of good cheer, for you, praise be to Allah, are much sought after." And she says: "I hear what you are saying." Ata (may Allah have mercy on him) also said: If she gave a man a promise during her waiting period and he then married her afterwards, they are not to be separated. [Hasan]
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14028