Bismillāh.
وَاذْكُرْ فِي الْكِتَابِ إِسْمَاعِيلَ ۚ إِنَّهُ كَانَ صَادِقَ الْوَعْدِ وَكَانَ رَسُولًا نَّبِيًّا
And mention in the book, Ishmā‘īl. Indeed, he was true to his promise, and an apostle and prophet.
Sūrat Maryam, No. 19, Āyat 54
According to narrations from the Ahl al-Bayt ‘alayhim al-salām, the Prophet Ismā‘īl mentioned in the above verse is not Ismā‘īl the son of Ibrāhīm (a). In addition to these narrations, the fact is further supported by how he is mentioned after Prophet Mūsā (a) in Sūrat Maryam. About a page or so earlier in the sūrah, Allah mentioned the prophets Ibrāhīm, Ishāq and Ya‘qūb (a). It would have been natural to mention Ismā‘īl the son of Ibrāhīm (a) at that point, rather than mentioning him after Prophet Mūsā (a).
This Ismā‘īl was another prophet, the son of Hizqīl himself also a prophet of Allah sent to the Banū Isrā’īl in the years after the death of Prophet Mūsā (a).
In a narration from Imām al-Ridā (a) he says:
Do you know why Ismā‘īl was called sādiq al‑wa‘d (true to his promise)? The narrator said: “I do not know.” The Imam then said: He once made a promise to a man and then sat waiting for him for a whole year, expecting his return.
While the period mentioned in this narration and others is an entire year, Shaykh Rizwan Arastu in his book God’s Emissaries has explained this as an exaggeration intended for emphasis, like how we would say “Sometime this century would be nice!” Otherwise, it is not feasible to imagine that he would have waited for one entire year. For example, he could have sent someone to remind the individual.
Regardless, the point of this attribute being mentioned by Allah is that He is clearly praising Prophet Ismā‘īl (a) for being true to his promise, thereby illustrating the importance of fulfilling one’s promise in Islam. Indeed, one of the greater sins in Islam is to break a promise or violate a pledge you have made, known in Arabic as naqd al-‘ahd or khulf al-wa‘d. In his famous letter to Mālik al-Ashtar, Imam ‘Alī (a) says:
Breaking one’s promise brings about hatred from God and from people. God the Exalted has said: ‘Greatly hateful it is in the sight of God that you say what you do not do.’ (Q 61:3)
It is worthy of mention that beyond the obvious situations of making a promise or a formal pledge with another person or even with Allah (the specific manner of which can be found in books of Islamic law), Islam also speaks of a covenant that all humans have by default made with Allah. In a higher realm known as ‘ālam-e dharr, where we existed in a certain form before descending into this lower material world, we all took a covenant with Allah that we would obey and worship Him. For example, in Q 36:60-61, Allah says:
أَلَمْ أَعْهَدْ إِلَيْكُمْ يَا بَنِي آدَمَ أَن لَّا تَعْبُدُوا الشَّيْطَانَ ۖ إِنَّهُ لَكُمْ عَدُوٌّ مُّبِينٌ وَأَنِ اعْبُدُونِي ۚ هَٰذَا صِرَاطٌ مُّسْتَقِيمٌ
Did I not make a covenant with you, O children of Adam, saying, “Do not worship Satan. He is indeed your manifest enemy. Worship Me. That is a straight path”?
There are also many narrations from the Ahl al-Bayt (a) to do with this covenant and the ‘ālam-e dharr. In the past, many Shī‘ah scholars with an intellectual inclination were unable to make sense of these narrations and rejected them. However, today because of Mulla Sadrā and the intellectual understanding of higher realms put forward by Islamic philosophy, these traditions are accepted by all Shī‘ah scholars and have become a standard aspect of Shī‘ah beliefs.
In any case, the lesson we would like to take from the above verse is the importance of fulfilling one’s word. Today we live in a time where one of the shameless and open policies of politicians is that they break their promise. It is no longer expected that a politician will abide by his campaign promises that he makes! As Muslims we must take heed from the above verse and be people who are true to our word. May we always by our word and uphold our promises regardless of who we make them to, friend or foe.
Sources: ‘Allāmah Muhammad Husayn Tabātabā’ī, Tafsīr al-Mīzān; Rizwan Arastu, God’s Emissaries.